ministry of agriculture, food and fisheries

$75.00 + GST

Ministry of Agriculture,Food and Fisheries

Comprehensive AutomationSystems

Climate Control

Irrigation

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Featuring:

Take Control With Argus

Call toll free: 1-800-667-2090

1-604-538-3531

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GRAPHICAL ANALYSIS

DATA RECORDING

Horticultural Training in

British Columbia

There are several universities and colleges in B.C. providing

introductory horticulture courses, including greenhouse

technician programs. Contact one in your area as a source

of trained staff for temporary or permanent assistance

and to obtain formalized training for your existing staff.

Following is contact information for the schools currently

offering general horticulture or pest management with

some greenhouse production classes.

Camosun University College

Victoria 250-370-3822

www.camosun.bc.ca/schools/tradesntech/horticulture

Kwantlen University College

Langley 604-599-3254, 604-599-2245

www.kwantlen.bc.ca/horticulture

Malaspina University College

Nanaimo 250-754-8756

www.mala.ca/horticulture

Okanagan University College

Kelowna 250-862-5457

www.ouc.bc.ca/trades/horticulture

North Island College

Courtenay 250-334-5000 ext.4602

www.nic.bc.ca

Simon Fraser University

Burnaby 604-291-4475

www.sfu.ca/biology

University College of the Cariboo

Kamloops 250-828-5181

www.cariboo.bc.ca

University College of the Fraser Valley

Chilliwack 604-795-2813

www.ucfv.ca/agriculture

University of British Columbia

Vancouver 604-822-1219

www.agsci.ubc.ca

Growing Greenhouse Peppers inBritish Columbia

A production guide for commercial growers ©

Published 2005 by

BC Greenhouse Growers’ Association108–7565 132nd Street

Surrey, BCV3W 1K5

and

Province of British ColumbiaMinistry of Agriculture, Food and Fisheries

PO Box 9120 - STN PROV GOVTVictoria, BCV8W 9B4

www.bcgreenhouse.ca

phone: 604 591-5480

fax: 604 591-5485

Copies of this publication are available at

$75.00 Cdn (plus 7% GST in Canada) plus shipping.

Contact the BCGGA office for details.

Ministry of Agriculture,Food and Fisheries

Growing Greenhouse Peppers in British Columbiaii

Library and Archives Canada Cataloguing in Publication DataMain entry under title:Growing greenhouse peppers in British Columbia. — 2004-

Irregular.“A production guide for commercial growers.”Co-published by Ministry of Agriculture, Food and Fisheries.ISSN 1712-4484 = Growing greenhouse peppers in British

Columbia

1. Peppers - British Columbia. 2. Sweet peppers - BritishColumbia. 3. Peppers - Diseases and pests - Control - BritishColumbia. 4. Greenhouse management — British Columbia.I. British Columbia. Ministry of Agriculture, Food and

Fisheries. II. BC Greenhouse Growers’ Association.

SB351.P4G76 635'.643’09711 C2004-960148-2

Growing Greenhouse Peppers in British Columbia iii

Acknowledgements

This publication was prepared over a period of several years and with contributions from many individuals. It

was originally conceived as an expansion of the pepper section in the 1996 Greenhouse Vegetable Production

Guide for Commercial Growers. Credit for much of the framework, therefore, lies with those who worked on

earlier versions of the various production guides that were published for many years by the B.C. Ministry of

Agriculture, Food & Fisheries. In the current edition, some contributed greatly and others less so. However, all

contributions, including those of people whose names have inadvertently been left off the list,

are greatly appreciated.

Principal Writers

Jim Portree, Anna Luczynski

Technical Advisors

Dave Ehret, Dave Gillespie, and Dave Raworth, Pacific Agri-Food Research Center, Agassiz B.C.;

Andrea Buonassisi, formerly with B.C. Ministry of Agriculture, Food & Fisheries;

Peter Isaacson, formerly with BC Greenhouse Growers’ Association.

Grower Advisors

Les Bohna, 635297 B.C. Ltd.

Jos DeGroot, formerly with South Alder Greenhouses;

Bram Moerman, Mt. Lehman Greenhouses;

Harmeet Atwal, Atwal Farms.

IPM Reviewers

Maria Keating, Andrea Davenport, Don Elliott.

Production

Edited by: Dave Ormrod.

Published by: Glenridge Graphics.

Special Thanks

Bob Costello, Jennifer Curtis, Elizabeth Hudgins, Linda Sawatzky, and Madeline Waring, BCMAFF;

Brian Spencer, Applied Bionomics;

Richard Ward and Chris Daye, BioBest;

Richard GreatRex and Dan Cahn, Syngenta Bioline;

Ronald Valentin, FOLIERA;

Angela Hale, Bug Factory;

Tineke Goebertus, Vortus;

Jim Matteoni, Kwantlen University College;

Chris French and Raj Utkhede, Pacific Agri-Food Research Centre, Summerland and Agassiz;

Irene Wilkin and Susan Garnett, Pest Management Regulatory Agency;

Zamir Punja, Simon Fraser University;

Aoxiang Shi;

Carol Portree.

Growing Greenhouse Peppers in British Columbiaiv

Using This Publication

This publication is intended as an aid to greenhouse pepper production in British Columbia and else-

where. The information presented replaces that given in the BC Greenhouse Vegetable Production Guide

that was last published in 1996. All of the information included was believed to be accurate and up-to-

date at the time of publication. However, errors are possible and changes in regulations and advances in

research occur over time. Growers are advised to double check any recommendation that appears to be

unusual or contrary to accepted practice. Many specific recommendations are given but these are in-

tended only as examples. Results will vary with each greenhouse and cultivar. Always experiment on a

small scale before making radical changes to currently successful practices. Consult seed companies and

bio-control suppliers for specific recommendations for the products that they provide.

All Rights Reserved

No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form

without the written permission of the BC Greenhouse Growers’ Association.

Disclaimer

While every care has been taken to ensure the accuracy of information, the BC Greenhouse Growers’

Association will accept no liability whatsoever for any inaccuracy or statement contained within this

publication.

Growing Greenhouse Peppers in British Columbia v

TABLE OF CONTENTS

1.1.1.1.1. HHHHHooooow the Pw the Pw the Pw the Pw the Plant lant lant lant lant WWWWWorororororks – Pks – Pks – Pks – Pks – Plant Plant Plant Plant Plant Prrrrrocessesocessesocessesocessesocesses ...............................................................................................................................................................................................................................................................................................................................................................................................................................1Introduction ........................................................................................................................................ 1Photosynthesis – Assimilate Production ............................................................................................. 1Respiration – Assimilate Break-down ................................................................................................. 2

Climate Control Factors Affecting Respiration .............................................................................. 2Uptake of Water and Nutrients .......................................................................................................... 2

Factors Affecting Uptake of Water and Nutrients .......................................................................... 3Transpiration ....................................................................................................................................... 4

Evaporation ..................................................................................................................................... 4Cooling the Tissue .......................................................................................................................... 4Movement of Water and Minerals ................................................................................................. 5Environmental Factors Affecting Transpiration .............................................................................. 5

Fruit Set and Development ................................................................................................................. 5Flower – Its Parts and Functions .................................................................................................... 5Fruit – Its Parts and Functions ....................................................................................................... 6

2.2.2.2.2. “Reading the Plant”“Reading the Plant”“Reading the Plant”“Reading the Plant”“Reading the Plant” ................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................9Partitioning of Assimilates ................................................................................................................... 9Plant Balance ..................................................................................................................................... 10Control Strategies for Adjusting Plant Balance ................................................................................. 10

Control Strategies Related to Changes in Production of Assimilates .......................................... 10Control Strategies Related to Changes in Sink Strength of Individual or Groups of Plant Parts 10Summary of Cause and Control of Unbalanced Growth ............................................................. 11

3.3.3.3.3. Optimizing the Greenhouse EnvironmentOptimizing the Greenhouse EnvironmentOptimizing the Greenhouse EnvironmentOptimizing the Greenhouse EnvironmentOptimizing the Greenhouse Environment ...................................................................................................................................................................................................................................................................................................................................................................................................... 15Introduction ...................................................................................................................................... 15Light .................................................................................................................................................. 15

Terminology and Measurements .................................................................................................. 15Variation in Light Intensity .......................................................................................................... 16Light Management ....................................................................................................................... 16

Temperature ...................................................................................................................................... 17Concept of Average Daily (24 hours) Temperature (ADT) ......................................................... 17Distribution of Temperature Over 24 Hours ............................................................................... 17

Influence of Temperature Control on Pepper Growth ...................................................................... 18Effect of Temperature on Vegetative or Generative Growth ........................................................ 18Effect of Temperature on Fruit Development and Quality .......................................................... 18Effect of Temperature on Partitioning of Assimilates ................................................................... 18

Equipment for Temperature Control ................................................................................................ 19Rail Pipe ....................................................................................................................................... 19Grow Pipe ..................................................................................................................................... 19

Venting .............................................................................................................................................. 20Moveable and Fixed Screens ......................................................................................................... 21Whitewash, Fog and Roof Sprinklers ........................................................................................... 21

Growing Greenhouse Peppers in British Columbiavi

Humidity ........................................................................................................................................... 22Terminology .................................................................................................................................. 22Measurements of RH, VPD and MDLA ..................................................................................... 22Role of RH, VPD, and MDLA in Managing an Active Climate ................................................. 22Role of RH and VPD in Management of Condensation (Dew Point) ........................................ 23

Control of Humidity ......................................................................................................................... 23Removing Humidity From Greenhouse Air ................................................................................ 23Seasonal Changes Affecting Control of Humidity ....................................................................... 24Daily Changes Affecting Control Strategies ................................................................................. 25

Avoiding Condensation – Dew Point ................................................................................................ 26Preventing Condensation During Plant Activation ..................................................................... 26Preventing Condensation Due to Radiation Loss ........................................................................ 26Distribution of Humidity and Temperatures .............................................................................. 27

Carbon Dioxide ................................................................................................................................. 27Introduction ................................................................................................................................. 27Sources of CO

2............................................................................................................................. 27

Measuring CO2 Applications ....................................................................................................... 27

Principles of CO2 Control ................................................................................................................. 28

Seasonal and Daily Strategies for CO2 Enrichment .......................................................................... 28

Economics of CO2 Enrichment .................................................................................................... 29

Design and Calibration of CO2 Delivery System ........................................................................ 30

Sensor Calibration ........................................................................................................................ 30Using Heat Storage to Optimize Use of CO

2.............................................................................. 31

Air Pollutants ..................................................................................................................................... 31Sources of Air Pollution ................................................................................................................ 31Common Pollutants ...................................................................................................................... 31Symptoms of Tissue Damage ....................................................................................................... 32Measurement and Detection of Air Pollutants ............................................................................ 32Strategies for Preventing Air Pollutant Damage ........................................................................... 33

Irrigation and Nutrition .................................................................................................................... 33Volume and Frequency of Irrigation Cycles ................................................................................. 33Control of Irrigation ..................................................................................................................... 34Effects of Excessive Frequency and Inadequate Volume of Irrigation .......................................... 36

Irrigation Design and Layout ............................................................................................................ 36Nutrition ........................................................................................................................................... 38

Tanks and Fertilizer Mixing .......................................................................................................... 38Electrical Conductivity (EC) ............................................................................................................. 39

Measurement and Interpretation of EC Value ............................................................................. 39Seasonal and Daily Trends in EC ................................................................................................. 40Effect of EC on Growth Balance .................................................................................................. 40Effect of EC on Taste and Shelf Life ............................................................................................. 40Monitoring Crop Nutrition ......................................................................................................... 40The pH ......................................................................................................................................... 41Measuring and Buffering the Feed Solution ................................................................................ 41

Water Quality .................................................................................................................................... 42Key Unwanted Ions ...................................................................................................................... 42Water Sources ............................................................................................................................... 42

Growing Media ................................................................................................................................. 44Media for Propagation .................................................................................................................. 44Properties of a Good Growing Medium ...................................................................................... 44

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4.4.4.4.4. PPPPPepper Pepper Pepper Pepper Pepper Prrrrroductionoductionoductionoductionoduction ................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................47Cultivars ............................................................................................................................................ 47Propagation ........................................................................................................................................ 47

Virus Susceptibility ...................................................................................................................... 47Time of Seeding ............................................................................................................................ 48Seed Germination ......................................................................................................................... 48Planting Into Block ...................................................................................................................... 48Transferring to Greenhouse .......................................................................................................... 49Acclimatization in the Production Greenhouse ........................................................................... 49

Crop Management ............................................................................................................................ 50Planting Density .......................................................................................................................... 50Stem Densities .............................................................................................................................. 50Training and Pruning in the Two-stem System ........................................................................... 50Management of Extra Stems in the Two-stem System ................................................................. 51Pollination ..................................................................................................................................... 51Harvesting ..................................................................................................................................... 51Storage .......................................................................................................................................... 52

Seasonal Management Strategies ....................................................................................................... 52Winter Production ............................................................................................................................ 53Spring Production ............................................................................................................................. 59Spring-Summer Production .............................................................................................................. 64Fall Production .................................................................................................................................. 70

5.5.5.5.5. PPPPPest and Dest and Dest and Dest and Dest and Disease Misease Misease Misease Misease Managementanagementanagementanagementanagement ................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 7575757575Integrated Pest Management (IPM) for Insect and Mite Pests ........................................................ 75

Monitoring ................................................................................................................................... 75Cultural Control ........................................................................................................................... 76Biological Control ......................................................................................................................... 76

Quality Control for Commercially Available Biologicals .................................................................. 77Chemical Control .............................................................................................................................. 78Greenhouse Cleanup and Other Factors Affecting Insect & Mite Survival ...................................... 78

Host Quality ................................................................................................................................ 79Weeds ............................................................................................................................................ 79Debris ........................................................................................................................................... 79Stages in Cleanup ......................................................................................................................... 79

The Major Insect and Mite Pests ...................................................................................................... 80Aphids ........................................................................................................................................... 80Fungus Gnats ............................................................................................................................... 90Loopers ......................................................................................................................................... 91Lygus Bugs .................................................................................................................................... 95Psyllids .......................................................................................................................................... 97Thrips ........................................................................................................................................... 98Two-spotted Spider Mite ...........................................................................................................101Whitefly ......................................................................................................................................107Miscellaneous Pests .....................................................................................................................108

Rodents ............................................................................................................................................110Field Mice (Voles) .......................................................................................................................110

Disease Management .......................................................................................................................112Fungal Diseases of Sweet Pepper .....................................................................................................113

Damping-Off ..............................................................................................................................113

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Fusarium Stem and Fruit Rot ....................................................................................................115Grey Mould ................................................................................................................................117Powdery Mildew .........................................................................................................................119White Mould ..............................................................................................................................120Storage Rots ................................................................................................................................121

Bacterial Diseases of Sweet Pepper ..................................................................................................121Bacterial Soft Rot ........................................................................................................................121

Virus Diseases of Sweet Pepper .......................................................................................................122Pepper Mild Mottle Virus ..........................................................................................................122Tobacco Mosaic Virus (TMV) and Tomato Mosaic Virus (ToMV) ..........................................123Tomato Spotted Wilt Virus (TSWV) .........................................................................................124

Physiological Disorders of Sweet Pepper .........................................................................................125Blossom-end Rot ........................................................................................................................125Sunscald ......................................................................................................................................126Shrink Cracks ..............................................................................................................................126Misshapen Fruit (knots) .............................................................................................................127Internal Growths and Wings ......................................................................................................127Tails .............................................................................................................................................127Cuticle Cracking .........................................................................................................................127

Greenhouse Cleanup .......................................................................................................................129Sanitation ....................................................................................................................................129Weed Control .............................................................................................................................129Crop Cleanup .............................................................................................................................130Re-using Growing Media ...........................................................................................................131Steam Sterilization of Rockwool Slabs .......................................................................................133

6.6.6.6.6. Colour PhotosColour PhotosColour PhotosColour PhotosColour Photos

7.7.7.7.7. Chemical and Biological Crop ProtectionChemical and Biological Crop ProtectionChemical and Biological Crop ProtectionChemical and Biological Crop ProtectionChemical and Biological Crop Protection ............................................................................................................................................................................................................................................................................................................................................................................................ 135135135135135Canadian Legislation .......................................................................................................................135

Pest Control Products Act & Regulations ..................................................................................135The Food and Drugs Act ............................................................................................................135The Fisheries Act and Migratory Birds Regulations ..................................................................135Transportation of Dangerous Goods Act ....................................................................................135

British Columbia Legislation ..........................................................................................................136Pesticide Control Act and Regulations .......................................................................................136Workers’ Compensation Board ...................................................................................................136

Toxicity ............................................................................................................................................139Hazard Shapes and Symbols ...................................................................................................... 139Exposure .....................................................................................................................................139Hazard ........................................................................................................................................139

Poisoning and First Aid ...................................................................................................................139Symptoms of Pesticide Poisoning ...............................................................................................139Poison Control Centre ................................................................................................................139First Aid ......................................................................................................................................139

Protective Clothing and Equipment ...............................................................................................141Coveralls ......................................................................................................................................141Gloves .........................................................................................................................................141Boots ...........................................................................................................................................142Goggles and Face Shields ............................................................................................................142

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Hats ............................................................................................................................................142Aprons .........................................................................................................................................142Respirators ..................................................................................................................................142Protective Equipment for Fumigants, Smoke Bombs and Foggers ............................................142Cleaning Protective Clothing and Equipment ...........................................................................143

Personal and Environmental Safety Guidelines ..............................................................................143Buying Pesticides ........................................................................................................................143Transporting Pesticides ...............................................................................................................143Storing Pesticides and Shelf Life .................................................................................................143Mixing and Loading Pesticides ...................................................................................................144Applying Pesticides .....................................................................................................................144After Applying Pesticides ............................................................................................................144Disposal of Unwanted Pesticides ................................................................................................145Disposal of Containers ...............................................................................................................145Re-entry Restrictions ..................................................................................................................145Harvesting Restrictions ..............................................................................................................145

Special Environmental Precautions .................................................................................................146Protecting Fish and Other Wildlife ............................................................................................146Protecting Bees and Beneficial Insects .......................................................................................146Emergency Response ..................................................................................................................146

Properties of Chemical and Biological Crop Protection Products ..................................................147Fungicides and Bactericides .......................................................................................................147Insecticides and Miticides ..........................................................................................................148

Spraying Equipment .......................................................................................................................152Sprayer Basics .............................................................................................................................152High-Volume Spraying Equipment ...........................................................................................153Specialized Greenhouse Pesticide Equipment ............................................................................154Sprayer Components ..................................................................................................................155Mixing Chemicals .......................................................................................................................157Sprayer Cleaning ........................................................................................................................157

Sprayer Calibration ..........................................................................................................................157Set-Up.........................................................................................................................................158Selecting Spray Volume ..............................................................................................................158Selecting Nozzle Pressure ...........................................................................................................158Calibrating Boom Sprayers .........................................................................................................158Calibrating Hand Operated Sprayers .........................................................................................160

8.8.8.8.8. AppendixAppendixAppendixAppendixAppendix ....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................... 163163163163163Preparation of Nutrient Solutions ...................................................................................................163Useful Measurements ......................................................................................................................168Glossary ...........................................................................................................................................170Bibliography ....................................................................................................................................175Useful Publications ..........................................................................................................................177

9.9.9.9.9. Grower Bio-control & Spray RecordGrower Bio-control & Spray RecordGrower Bio-control & Spray RecordGrower Bio-control & Spray RecordGrower Bio-control & Spray Record ............................................................................................................................................................................................................................................................................................................................................................................................................................... 179179179179179

10.10.10.10.10. IndexIndexIndexIndexIndex ..................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................... 185185185185185

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LIST OF FIGURES

Figure 1-1. Transpiration and water uptake ........................................................................................ 4Figure 1-2a. Good quality flower ........................................................................................................ 5Figure 1-2b. Poor quality flower ......................................................................................................... 6Figure 1-3. Vertical and horizontal section of pepper fruit with good and poor pollination ............ 7Figure 3-1. Average daily temperature .............................................................................................. 18Figure 3-2a. Plant activation with minimum pipe temperature ...................................................... 20Figure 3-2b. Plant activation with maximum pipe temperature ...................................................... 20Figure 3-3. Seasonal humidity control by condensation and ventilation without screens .............. 25Figure 3-4. Influence of CO

2 concentration in the air on plant uptake ........................................... 28

Figure 3-5. Overdrain monitoring station ........................................................................................ 35Figure 3-6. Layout of a greenhouse irrigation system ....................................................................... 37Figure 3-7. Growing slab/drainage collection layout ....................................................................... 37Figure 3-8. How medium pH affects the availability of plant nutrients ......................................... 42Figure 5-1. Identification of the four aphid species found commonly on greenhouse peppers ....... 81Figure 5-2. Round, even-edged exit hole created by parasitoid and jagged-edged exit hole

created by a hyperparasitoid ........................................................................................................ 82Figure 5-3. Adult and larva of the fungus gnat, shore fly and moth fly ........................................... 90Figure 5-4. Adult Western Flower Thrips ......................................................................................... 98Figure 5-5. Differences in spider mite population growth .............................................................102Figure 5-6. Effectiveness of biological control mites with P. persimilis ..........................................103Figure 7-1. Pesticide warning symbols and shapes .........................................................................140Figure 7-2. Assembly of disc-core cone nozzle ................................................................................156

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Growing Greenhouse Peppers in British Columbia xi

LIST OF TABLES

Table 2-1. Description, possible causes and control approaches for unbalanced vegetative and generative growth ..... 12Table 2-2. Stress-related growth abnormalities ....................................................................................................... 14Table 3-1. Frequently used radiometric terms, definitions and units ....................................................................... 16Table 3-2. ADT (average daily temperature) calculation ......................................................................................... 17Table 3-3. Control of pepper “balance” in relation to temperature and light intensity .............................................. 19Table 3-4. Summary of seasonal venting strategies used for temperature control ...................................................... 22Table 3-5. Common water vapour terms and units used in greenhouse industry ..................................................... 22Table 3-6. The relationship between RH and temperature drop or differences that will cause condensation .............. 24Table 3-7. The relationship between VPD and temperature drop or differences causing condensation ..................... 24Table 3-8. Effects of seasonal climate conditions on methods of humidity control ................................................... 25Table 3-9. Principles of applying heat and ventilation for the control of seasonal and daily variations in humidity .... 26Table 3-10. Application rates and computer set points for CO

2 as related to seasonal and daily weather variations ..... 29

Table 3-11. General rule for estimating the % yield increase at different CO2 concentrations and light levels ............ 29

Table 3-12. Maximum acceptable concentrations of some noxious gases for humans and plants .............................. 32Table 3-13. Summary of seasonal and daily control strategies for irrigation timing, volume and frequency ................ 34Table 3-14. Distribution of the percentage over-drain during a sunny spring day ................................................... 35Table 3-15. Guideline for stock solutions of feeding formulas for peppers grown in sawdust and rockwool .............. 39Table 3-16. Seasonal range of EC targets for feed and drain ................................................................................... 40Table 3-17. Daily range in feed EC for bright and dull days .................................................................................. 40Table 3-18. Target over-drain levels in drain to waste and re-circulation system ....................................................... 41Table 3-19. Target levels for tissue analysis of sweet peppers ................................................................................... 41Table 3-20. Preferred nitrogen sources for pH control ............................................................................................ 42Table 3-21. BCMAFF Greenhouse irrigation water quality guidelines .................................................................... 43Table 4-1. Greenhouse Pepper Seed Suppliers ....................................................................................................... 47Table 4-2. Winter production cycle / December-January (up to week 4) ................................................................. 58Table 4-3. Early spring production cycle / February-March-April (weeks 5-18) ...................................................... 63Table 4-4. Late spring and summer production cycle / May-August (weeks 19-35) ................................................ 69Table 4-5. Fall production cycle / September-November (weeks 36-46) ................................................................. 73Table 5-1. Summary of IPM strategies for the green peach aphid ........................................................................... 83Table 5-2. Summary of IPM strategies for the foxglove, potato and melon/cotton aphid ......................................... 84Table 5-3. Commercially available biological control agents for aphid control .......................................................... 86Table 5-4. Commercially available biological control agents for fungus gnats ........................................................... 92Table 5-5. Commercially available biological control agents for cabbage looper ........................................................ 93Table 5-6. Commercially available biological control agents for thrips ................................................................... 100Table 5-7. Summary of seasonal monitoring and biological control strategies for the two-spotted spider mite .......... 104Table 5-8. Commercially available biological control agents for the two-spotted spider mite ................................... 105Table 5-9. Commercially available biological control agents for whitefly ............................................................... 109Table 5-10. Environmental factors favourable to disease development by Botrytis ................................................ 117Table 5-11. Time and temperature required to kill various pests and pathogens ..................................................... 133Table 7-1. List of pesticide common names, trade names and relative toxicity to mammals ..................................... 137Table 7-2. Typical droplet sizes for various types of pesticide spray applications ..................................................... 152Table 7-3. Comparison of specialized greenhouse sprayers .................................................................................... 154Table 8-1. Molecular weights for various fertilizers ............................................................................................... 165Table 8-2. Quantities of acids and salts to add to 1000 litres to make 100X stock solution .................................... 165Table 8-3. Quantities of salts to add to 1000 litres to make 100X stock solution ................................................... 165Table 8-4. Approximate quantities of iron chelates to add to 1000 litres to make 100X stock solution .................... 166Table 8-5. Quantities of minor elements to add to 1000 litres to make 100X stock solution .................................. 167Table 8-6. Useful measurements ......................................................................................................................... 168

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Growing Greenhouse Peppers in British Columbiaxii

INTRODUCTION

The greenhouse environment plays a primary

role in controlling yield, fruit quality, plant

balance and speed of growth. The profitability

of growing greenhouse peppers depends to a

great extent on the grower’s ability to maintain

an optimum environment for the plant.

Management strategies for all components of

the greenhouse environment (temperature,

humidity, vapour pressure deficit, carbon

dioxide, nutrition, irrigation and media) are

primarily defined by the seasonal and daily

changes in accumulated light. Plant balance

and speed of growth are equally important

aspects influencing climate control strategies.

This publication emphasizes the importance of

climate control and its impact on plant growth

and production. In the first three chapters, the

key aspects of climate control are presented,

each from a slightly different perspective. In

most cases, these principles apply to all green-

house vegetable crops. Chapters 4, 5 & 6 zero in

on the day-to-day specifics of greenhouse pepper

production. Chapters 7, 8 & 9 provide a wealth

of information useful not only to pepper growers

but to all greenhouse vegetable growers.

Section1. “How the Plant Works”, illustrates how

light, temperature, CO2 and other climate

factors affect basic plant processes.

2. “Reading the Plant”, discusses how

changes in climate control and cultural

practices affect plant balance (partitioning of

sugars).

3. “Optimizing the Greenhouse Environ-

ment”, presents management strategies for each

of the greenhouse climate factors: light, tem-

perature, humidity, CO2, irrigation and media.

4. “Pepper Production”, provides detailed

recommendations for pepper propagation

and production. Recommendations included

in this section emphasize issues related to

the four growing periods: winter, spring,

summer and fall and are non-specific for

cultivar differences.

5. “Pest and Disease Management”, gives

detailed descriptions of the various pests and

diseases affecting greenhouse peppers. Manage-

ment strategies emphasize methods that either

use or are compatible with biological and

cultural control.

6. “Colour Photos”, brings together a collec-

tion of photographs illustrating many of the

practices and problems associated with

pepper growing.

7. “Chemical and Biological Crop Protec-

tion”, provides details on the few pesticides

that are used on greenhouse peppers. Proce-

dures for the safe handling, storage and

effective use of pesticides are outlined.

8. “Appendix”, contains a wealth of informa-

tion useful to pepper growers and others.

Included are a glossary of terms, a bibliogra-

phy, tables of weights and measures, tables

for preparing nutrient solutions and a list of

useful publications.

9. “Grower Bio-control & Spray Record”,

provides templates for keeping records of

control activities.

Growing Greenhouse Peppers in British Columbia 1

1.

Ho

w t

he P

lan

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ork

s –

Pla

nt

Pro

cesses 1. HOW THE PLANT WORKS –

PLANT PROCESSES

light compensation point. It occurs at about2% of maximum light. A negative or break-even assimilate balance can occur during winterwhen light intensity is low and average dailytemperatures are relatively high. If not com-pensated, poor light conditions and sub-optimaltemperatures can halt plant growth and devel-opment. During winter frequent temperatureadjustment is required to maintain a positiveassimilate balance.

Light saturation is the point at which anyfurther increase in light intensity no longerincreases the assimilation rate. Pepper plantsare rarely light saturated, as most commercialoperations use screens when light intensity ismore then than 600 watts/m2 to protect thefruit from sunscald.

CO2

Although less important than light, CO2 con-

centrations have a significant effect on theproduction of assimilates. Regardless of lightintensity, assimilation increases with an in-crease in CO

2 concentration. Production of

assimilates is optimal when high lightintensities interact with moderate to highconcentrations of CO

2. The benefit of CO

2

enrichment is most apparent at low concentra-tions of CO

2 (350 to 500 ppm).

TemperatureTemperature has only a minor effect on photo-synthesis. Most greenhouses maintain theirlight hours temperatures between 20 to 25°C,which is the optimal temperature range forphotosynthesis.

Irrigation and HumidityAn interruption in water supply will reduce

Introduction

This section provides a short overview of eachof the fundamental plant processes that driveplant growth, development and maintenance:photosynthesis, respiration, transpiration,nutrient uptake, and fruit set and development.In each section, the key environmental factorssuch as: light, CO

2, temperature, vapour pres-

sure deficit, and nutrients that influence eachprocess are identified and discussed.

Photosynthesis –

Assimilate ProductionPhotosynthesis is the ‘anabolic’ or building upphase of plant metabolism. It uses light energy toconvert CO

2 into energy-rich molecules such as

sugars (assimilates). Assimilates can then beused as an energy source, or they can be con-verted to more complex molecules and structuralcomponents of the cell. Photosynthesis releasesoxygen gas, which is either re-absorbed during therespiration process (discussed later) or diffusedout through the leaves. The rate of photosynthesisis affected by: light, CO

2, temperature, water,

nutrient availability and leaf area.

LightThe amount of absorbed light (photo-synthetically active radiation or PAR), is themost important factor affecting the productionof assimilates.

At very low light intensity, assimilate produc-tion can be negative, i.e. there are more assimi-lates consumed than produced (the leaf respira-tion rate is higher then the photosynthesis rate).The point at which assimilate production isequal to assimilate consumption is called the

Growing Greenhouse Peppers in British Columbia2

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assimilate production by causing stomatalclosure and reduced CO

2 uptake. Reopening

of the stomata can take several hours. Exces-sive loss of water vapour (transpiration) by theleaves will also have the same result, causingflagging of the young leaves. Adequate volumeand proper timing of irrigation cycles willreduce the possibility of transpiration stress.

Nutrient AvailabilityMineral deficiencies, particularly nitrogen (N),which is an important component of the chloro-phyll molecule, may also reduce the assimilationrate. However, these limitations are usuallyconsidered secondary to light or CO

2.

Leaf Area Index (LAI)Leaf area can also affect assimilate production.The leaf area index (LAI) is the ratio of plantleaf area to ground area (m2leaf area/m2

ground area). Light interception is poor belowLAI 3 whereas above LAI 3, over 90% of lightis intercepted by the canopy. A fully developedpepper canopy, at LAI of 5 to 6, will havesimilar assimilation rates as plants at LAI 3.Assimilation capacity decreases with leaf age.

Respiration – Assimilate

Break-downRespiration is the ‘catabolic’ or breaking downphase of plant metabolism. It provides energyto drive growth and development of the plant.All living plant cells respire. It is a process inwhich mainly sugars, but also starch, fats, andother plant substrates are metabolized (brokendown) to provide energy. The process con-sumes O

2 and produces CO

2 and water.

Respiration takes place day and night in allcells. In the leaves, energy for respiration isprovided by photosynthesis during the day. Ingeneral, the catabolic rate of respiration is 10%of the anabolic rate of photosynthesis.

Energy released during respiration is used formaintenance and repair of existing cells; and todrive new cell growth. Maintenance respirationsupplies energy to take up minerals, pump out

toxins, repair cellular organs, and for other cellfunctions. Growth respiration supplies energyand the raw materials to build new cells.

In young plants, respiration rates are highduring rapid vegetative growth and reduced justbefore flowering. In mature plants, respirationrates remain high in the young leaves, roots,flowers and fruit. There is a direct and positivecorrelation between the growth rate of particu-lar cell types and their respiration rates, i.e.cells that respire a lot grow faster.

Climate Control FactorsAffecting Respiration

TemperatureRespiration responds instantly and strongly totemperature change, i.e. the rate of maintenanceand growth respiration increases with tempera-ture. Unlike photosynthesis, the rate of respira-tion quadruples within a temperature range of 5to 25oC and to a lesser degree between 30 to35oC. Plant growth increases directly in propor-tion to the increase in growth respiration. Tem-perature control is one of the most importanttools for controlling crop growth.

Other factors influencing respirationSeveral other factors may influence pepper plantrespiration rates. Respiration depends on a supplyof assimilates, therefore respiration rates in leavestend to be higher when they contain more assimi-lates, for example at dusk.

Uptake of Water andNutrients

RootsFine root hairs (1 to 4 cm from the growing tip)absorb most of the water and minerals. Theyexist for only a short period of time – from a fewdays to a few weeks. Continuous root growthand a large surface area of healthy fine roots arecritical for adequate water and nutrient supply.

The xylem and phloem conductive tissuesensure the flow of water, nutrients, and sapbetween the roots and leaves.


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In greenhouse vegetables, the following rootfunctions are of prime concern:

• absorption of water, minerals, and oxygenfrom the growing media; and

• conduction of water and nutrients (discussedin the transpiration section below).

Absorption of WaterThe driving force behind water uptake by theroots is the difference in water concentrationbetween the feed and the roots. Uptake of wateris a passive process that does not require energy.Water taken up by the roots is carried by thexylem to the leaves in the transpiration stream.

Absorption of NutrientsNutrient uptake is an active and energy con-suming process of maintenance respiration.

The roots absorb nutrients in the form ofcations (+) or anions (–). Each form can beabsorbed independently and in different quanti-ties. Mono-valent ions (e.g. NH

4

+, K+, NO3

-,Cl-) are taken up more readily than di-valentions (e.g. Ca++, Mg++). The uptake rate ofNH

4

+, NO3

-, Ca++, and K+ increases with theincrease in water uptake.

The uptake of an ion from the nutrient solutionis always followed by the release of an ion ofthe same charge to the nutrient solution. Forexample, the uptake of an anion (NO

3

-, H3PO

4

-,Cl-) is always balanced by the release of HCO

3

-

or HO- to the nutrient solution, whereas theuptake of a cation (NH

4

+, K+, Ca++) is bal-anced by the release of an H+ ion. Predomi-nant uptake of either cations or anions can,therefore, affect the pH of the rooting zone anddrain. For example, the pH of the drain can becontrolled by varying the proportions of ammo-nium and nitrate in the nutrient solution.Plants have a strong preference for ammoniumand will take most of the NH

4

+ up beforetaking NO

3

-. Uptake of NH4

+ will decrease thepH in the rooting zone and drain by increasingthe concentration of H+.

The nitrogen (NO3 and NH

4) absorbed by the

roots needs to be converted to organic com-pounds before being transported to the leavesand fruit. This process requires a substantialamount of maintenance energy.

Absorption of OxygenAll living cells, including those in the rootsmust have oxygen for maintenance and growthrespiration. Roots secure oxygen from waterand air found in the pore spaces of the rootingmedia. Low oxygen concentrations in thegrowing media will reduce root respiration.This negatively impacts activities such asmineral uptake, nitrogen assimilation and rootgrowth. As they age, roots will respire less andtherefore absorb less oxygen.

Factors Affecting Uptake ofWater and Nutrition

Light and CO2: affect root function indirectly,

through their affect on assimilate availability.Optimal root growth and function depend onthe availability of assimilates. Under low lightintensity and CO

2 concentration, the produc-

tion of assimilates is reduced. Roots areweaker competitors for assimilates than rapidlygrowing fruit. The supply of assimilates to theroots will fluctuate depending on assimilateavailability and demand by other plant parts.Theses fluctuations contribute to stalled andrenewed growth cycles.

EC and pH: roots function well in a wide range.The absorption of nutrients is optimized withinpH 5.8 to 6.2 and EC 1 to 6 mS/cm. A loweror higher pH can hamper the uptake of selectedions. Sudden changes in the EC or pH, such asflushing the growing media with water, cancause irreversible damage to the fine roots.

Temperature of the nutrient solution: has a majoreffect on root growth. During early vegetativegrowth, the irrigation temperature of the growingmedia should be maintained at 20 – 21oC toencourage root growth. Once the roots areestablished, the temperature should be loweredto16 or 18oC to optimize oxygen uptake.


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Root-dieback: symptoms range from minordiscolouration of the root tips to the moreevident browning and decaying of large rootsections. Healthy roots appear white, firm andfibrous. Aboveground symptoms of root die-back range from a temporary lightened leafcolour to mild chlorosis in the head. This is theresult of a reduced or halted uptake of microand macro-elements; their absorption is de-pendent on healthy root tips. Plant “flagging”during mid-day is another possible sign of rootdie-back. Loss of roots has a direct and nega-tive bearing on plant balance, speed of growth,fruit set, and fruit quality. Root die-back canbe caused by a shortage of assimilates, a lackof oxygen or disease.

TranspirationTranspiration is the process of water evaporat-ing from the leaves, usually through the sto-matal openings. Transpiration enables thedistribution of water and nutrients through theplant and cools the plant tissue.

Evaporation

Water evaporates because the greenhouse air isalways drier than the air in the stomata, whichis always at 100% relative humidity (RH). Thedegree of difference between the water vapourconcentration in the greenhouse air and sto-mata air determines the transpiration rate i.e.the drier the greenhouse air, the higher thetranspiration rate.

Commercial greenhouses use the vapour pres-sure deficit (VPD) to estimate the transpirationrate. The VPD doesn’t measure, however, theconcentration of water vapour in the leafstomata. During winter and early spring, theleaf temperature and air temperature during theday is about equal. Under these circum-stances, the VPD of the greenhouse air ad-equately illustrates the transpiration rate.During late spring and summer, the leaf tem-perature may exceed the air temperature by afew degrees and the transpiration rates will behigher than those estimated by the VPD. Cli-

mate and irrigation strategies should compen-sate for a higher transpiration rate.

As the transpiration rate increases with increasedlight intensity in the morning, there is a delay ofup to several hours before water uptake by theroots will keep pace with water lost throughtranspiration (see Figure 1-1). As a result, thewater content of plant tissue is lower during theday than at night. In the late afternoon, assunlight is reduced, the transpiration rate drops,but water uptake continues at a high rate replen-ishing tissue to overnight water levels.

A plant with a high transpiration rate may besusceptible to water stress when water uptakefrom the roots cannot keep up with water lossthrough transpiration. The immediate effect ofa mild case of water stress is slowed growth(speed). Under severe stress, the stomata closeand limit assimilate production.

Cooling the Tissue

Transpiration cools the leaves, which is impor-tant during periods of high temperatures. Goodmaintenance of an ‘active’ plant, i.e. one that istranspiring rapidly, ensures optimal tissuetemperature and prevents stomatal closure.

Figure 1-1. Transpiration and water uptake


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Movement of Water andMinerals

As water evaporates from the interior of theleaf, more water is drawn up from the roots,through the xylem. A transpiration stream,which moves water and minerals from rootsthrough the plant to the leaves, is created.

Distribution of Calcium Withinthe PlantAll nutrients are carried in the transpirationstream (xylem) in very low concentrations.When the transpiration stream is idle or exces-sive, the plant can use the phloem conductivetissue as a back up system for nutrient distribu-tion. Calcium and boron are the only twonutrients that are restricted to transport in thexylem only.

The lack of calcium distribution via the phloemto small fruit is one reason for blossom-end rot(BER).

During high transpiration, the movement ofwater and calcium is directed primarily to theleaves. Fruit transpires at a lesser rate thanleaves and the supply of water and most of thenutrients to the fruit occurs mainly throughphloem. This can limit calcium supply to theblossom end of the fruit, causing the formationof brown leathery tissue (BER).

Environmental FactorsInfluencing Transpiration

Light: is directly related to the transpirationrate; the higher the light intensity, the greaterthe transpiration rate. At excessive transpira-tion rates, water loss can exceed water uptake(water stress) causing stomatal closure andlimiting photosynthesis and nutrient uptake.

Temperature: in the absence of light, can affectplant transpiration. Transpiration rates increasewith an increase in leaf temperature. Above30oC, however, the stomata close, resulting inreduced transpiration.

CO2: at high levels reduces transpiration.

Although the stomata close significantly whenexposed to high levels of CO

2 the effect is

relatively small, possibly due to the interactionof other environmental factors.

Humidity: the lower the humidity (higherVPD), the greater the transpiration rate. This isbecause the gradient for water vapour move-ment from leaf to air is steeper. If humidity istoo high (low VPD) water flow in the xylemfrom the roots to the leaves is reduced.

Irrigation: must be adequate; inadequate orirregular water supply can cause water stressresulting in stomatal closure and reducedtranspiration.

Fruit Set and

Development

Flower – Its Parts and Functions

The pepper plant produces single white flowersthat sit in the axils of the branches or leaves.Small flowers (up to 2.5 cm) set in the primaryaxils, produce the best quality fruit. A goodquality flower is small, bent downwards at a90° angle, and has a thick stem (peduncle) (seeFigure 1-2a).

Figure 1-2a. Good quality flower


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The flower has five stamens ( ) each contain-ing a pollen sac (anther). The pistil ( ) consistsof a pollen-receptive stigma, a connective styleand an ovary that develops into the pepper fruit.

The pepper flower is primarily self-pollinatingbut cross-pollination does occur. Successfulself-pollination depends on the viability of thepollen, a downward bending (90o) position ofthe flower and the optimal alignment of thestigma and pollen sacks. An upright position ofthe flower or excessively long pistil will preventpollen from landing on the stigma (see Figure1-2b). Pepper fruit can develop without fertiliza-tion but the fruit will be seedless (parthenocarpic)and small with thin walls.

Pepper flowers secrete nectar from the base ofthe petals. The nectar consists mainly offructose. Bees and other pollinators visit theflowers but the attractiveness of this nectar isrelatively low.

Flower Initiation

Peppers initiate many more flowers then thenumber that actually set fruit (10 to 15%).

Temperature has a major affect on flowerinitiation. Flower initiation increases withincreased average 24-hour temperatures (ADT).A large spread between day and night tempera-tures also increases flower initiation.

Growers often apply one or a combination ofthe following measures to promote flowerinitiation:

• Increase the EC;

• Decrease the frequency and increase thevolume of an individual irrigation cycle;

• Increase the concentration of CO2.

Fruit – Its Parts and Functions

All bell-type cultivars are recognized by thelarge blocky appearance of their fruit, promi-nent shoulders, inner partitioning (locules), andblunt or sunken fruit end (apex). Bell peppersmay have two to four locules; the fruit withfour-locules has the highest market value. Thefruit walls (pericarp) are thick-fleshed. Thenumber of locules, shape of fruit and numberof seeds are directly related to the extent ofsuccessful pollination (see Figure 1-3).

Fruit SetClimatic factors such as light intensity or CO

2

concentrations affect the availability of assimi-lates and have an indirect but important effecton fruit setting. Flowers store assimilatesduring the day and metabolize them during thenight. The shortage of assimilates is the pri-mary factor determining flower and fruit abor-tion. Low temperatures at night (17 to 19oC)can increase the percentage of fruit set.

Fruit AbortionTemperature has an indirect but significanteffect on the abortion of flowers and earlystage fruits. If the ADT is too high, fruitsetting will be reduced or prevented. Theabortion of flowers or small fruit (<2 cm) iscaused mainly by a shortage of assimilates.High temperatures reduce the export of assimi-lates from the leaves and increase the totaldemand for assimilates by vegetative andgenerative plant parts. As a result there isreduced assimilate flow to the flowers and earlyfruit stages and increased chance of abortion.

Fruit load and the fruit development stage canalso affect the incidence of abortion. Fruits at

Figure 1-2b. Poor quality flower


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the swelling green stage, particularly ones withhigh seed counts, are much stronger competi-tors for assimilates than those at earlier stages.Developing fruits also produce plant growthregulators that can inhibit subsequent fruit set.

Fruit abortion is enhanced by:

• high night temperature;

• high temperature (20 to 24oC) combinedwith low light intensity;

• above threshold concentrations of pollutantsin the greenhouse air;

• pests and diseases.

Fruit QualityFruit quality is affected primarily by pollina-tion, availability of assimilates, temperatureand availability of nutrients.

1. Pollination: increases seed count which inturn increases the ability to draw assimilates,increases fruit size and weight, reducesnumber of malformed fruits. Temperature

and relative humidity affect pollen viability. Ata temperature range of 20 to 22oC, pollenviability is optimized whereas low night tem-peratures (12 to 16oC) or high day temperatures(>28oC) significantly reduce its viability.Pollen viability and seed set decreases withdecreasing relative humidity (RH).

2. Availability of assimilates: limited or exces-sive supply of assimilates can negativelyaffect flower quality and subsequent fruitquality. Excessive competition between fruitscan reduce the availability of assimilates.

3. Temperature: at high temperatures (>25oC),fruit will mature faster but will have thinnerwalls and lower weight; at lower tempera-tures, especially during the night, fruit willdevelop thicker walls and be heavier.

4. Availability of nutrients: calcium (Ca++) distri-bution to the fruit is reduced with high transpi-ration. This is especially critical at the small(<2 cm diameter) early stage where a shortageof calcium causes blossom-end rot (BER).

Figure 1-3.

Vertical and horizontal section of pepper fruit with good pollination

Vertical and horizontal section of pepper fruit with poor pollination


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Partitioning of AssimilatesAssimilates produced in leaves are either storedin storage pools or distributed within the plantto support plant growth and maintenance.Distribution of assimilates within the plant isprimarily regulated by two components:

• the number of sinks demanding assimilates,including all vegetative and generative plantparts such as leaves, head, side shoots, roots,flowers and fruit; and

• the degree of strength with which each sinkdraws assimilates.

The two components combined, i.e. the aggre-gate strength of all sinks, makes up the totaldemand for assimilates within the plant.

The growth rate of an individual plant part isdetermined by its sink strength; the stronger thedemand for assimilates the faster the growthrate. Some of differences in sink strength areinherent but some are due to: the proximity ofthe sink to the assimilate producing leaves, thecourse of organ development, and nature ofthe growing season.

Roots are inherently weak competitors forassimilates. They are located far away fromleaves which is thought to diminish theirstrength for demanding assimilates; conse-quently they grow at a slower rate than stems,leaves or fruits. At the beginning of fruitproduction, root growth is strongly reduced; athigh fruit load, it can even be stalled. In severecases, the root tips may die.

In contrast, pepper fruits compete strongly witheach other and with vegetative parts of the

plant for the available assimilates. At high fruitload, fruits are a strong and highly preferentialsink for assimilates and substantially reduce theflow of assimilates to the vegetative growth.

The strength with which pepper fruit drawassimilates depends mainly on:

Developmental Stage of the FruitPepper fruit passes through three stages: newlyset fruit (< 2 cm), green swelling and colour.The demand for assimilates and the growth ratevary at each stage. Newly set fruit and colourstages demand relatively small amounts ofassimilates and are considered weak sinks. Thegreen swelling stage demands more assimilatesand is considered a strong sink. Maintaining arange of fruit developmental stages on theplant prevents excessive competition for as-similates and prevents fruit flushes.

Number of Developed SeedsFruits with high seed counts are larger and havestronger demand for assimilates than fruits withlow seed counts. Although an increase in thesink strength improves the quality of the indi-vidual fruit, it draws assimilates away fromyoung fruits and flowers. As a result, there couldbe more aborted flowers and more irregularities(flushing) in fruit production.

Position of the Fruit Within the PlantCanopyFruits set on the main axis are larger and betterquality than fruits set on a secondary axis. Thedifference in sink strength could be attributedto the fact that the secondary fruit is furtheraway from assimilate-producing leaves.


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Plant BalanceA pepper plant is considered to be in balancewhen available assimilates support: (1) suffi-cient vegetative growth to maintain futuregrowth potential; and (2) optimal generativegrowth to maximize yield. A plant is too veg-etative when assimilates available are usedpredominantly to support the growth of head,shoots and roots. A plant is too generativewhen assimilates are used predominantly tosupport generative growth.

Plant balance is affected primarily by theamount of assimilates available and totaldemand for assimilates by all the vegetative andgenerative plant parts. Plant balance can changein response to a change in the amount ofassimilates produced and a change in the as-similate- drawing strength of one or moresinks. Different control strategies are requiredfor each situation.

Control Strategies for

Adjusting Plant Balance

Control Strategies Related toChanges in Production ofAssimilates.

Accumulated light and the resulting assimilateproduction varies both seasonally and daily.Adjustment of the speed and direction of plantgrowth requires long and short-term manage-ment strategies in response to changing assimi-late production.

Long-term StrategiesDuring winter, young pepper plants producerelatively small amounts of assimilates becausetheir leaf area is still very small and the accu-mulated light is low. Most assimilates producedduring the first few weeks are partitionedamong the vegetative parts to promote rapidincrease in leaf formation and among the rootsfor establishment of a strong root system. Thisstrategy quickly increases leaf area and lightinterception, and consequently, the production

of assimilates. Fruit should be allowed to setonly after enough assimilates are produced tosupport both vegetative and generative growth.

During spring and early summer, accumulatedlight and potential for assimilate productionincreases. In response to the seasonal increasein accumulated light, commercial greenhousesprogressively increase fruit loads per m2.

Short-term StrategiesAccumulated light and the resulting assimilateproduction fluctuate daily. Managing tempera-ture inside the greenhouse is one of the mostimportant tools in controlling the assimilatedistribution between the vegetative and repro-ductive parts of the plant.

A change in the average 24-hour temperature(ADT) will cause a proportionate increase ordecrease in the consumption of assimilates. Mostassimilates will be drawn to the strongest sinksand less will be distributed to the weaker ones.Increased ADT during fruit production will causea higher assimilate flow towards the fruit ratherthan vegetative parts of the plant. The directionand degree of temperature change should alwaystake into consideration the amount of assimilatesproduced the previous day.

A temperature drop during pre-night will createa temperature difference between the fruit andthe remaining plant parts. A warm fruit willmaintain a higher demand for assimilates for alonger period of time (See Temperature Con-trol, page 18).

Control Strategies Related toChanges in Sink Strength ofIndividual or Groups of PlantParts.

Fruit set, abortion, harvest and selective prun-ing can strongly change the distribution ofassimilates between the vegetative and genera-tive parts and affect plant balance.


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Fruit Setting and AbortionSetting new fruit is an important tool in re-directing the flow of assimilates toward genera-tive growth. Newly set fruit demands a rela-tively small amount of assimilates from theplant and more fruit may set than will mature.Thinning extra fruit can be used to controlplant balance but timing is very important.Thinning the fruit too early may cause the plantto start setting again.

If fruit set is too high, it can reduce the avail-ability of assimilates for the next fruit set andfor vegetative growth resulting in a plant that istoo generative. A compacted head and ashortened distance between the flower andhead are typical symptoms of a plant that is toogenerative.

Fruit HarvestThe plant balance can change momentarilywhen the mature fruit is harvested. To preventa dramatic shift in assimilate partitioning,

maintain as uniform a harvest as possible.Harvesting too many fruit will negatively affectthe plant balance and may cause root die-back.

Selective PruningTotal sink strength increases with an increaseof fruit on the plant. If the fruit load is toohigh in relation to the amount of assimilatesproduced, pruning the mature green fruit maybe necessary to restore plant balance. Harvest-ing mature green fruit will often induce a newflush of fruit set.

Summary of Cause and Controlof Unbalanced Growth

Table 2-1 summarizes symptoms of unbalancedgrowth, possible causes and suggested controlstrategies. Table 2-2 lists additional abnormali-ties in growth and suggests some correctiveapproaches.


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Tab

le 2

-1.

Des

crip

tio

n, p

oss

ible

cau

ses

and

co

ntr

ol a

pp

roac

hes

fo

r u

nb

alan

ced

veg

etat

ive

and

gen

erat

ive

gro

wth

.

Str

on

gly

Veg

etat

ive

Str

on

gly

Gen

erat

ive

Description T

all p

lant

with

str

ong

side

sho

ots

and

larg

e le

af a

rea

(> 6

m2 le

af/m

2 gr

ound

are

a).

Pla

nt h

as lo

w fr

uit l

oad

with

mor

e th

an 5

leaf

nod

es b

etw

een

sets

. H

igh

inci

denc

e of

flow

er a

bort

ions

.

Ope

n pl

ant w

ith s

mal

l lea

f are

a (3

to 5

m2 le

af/m

2 gro

und

area

).

Fru

it lo

ad h

ighe

r th

an 3

5 m

2 and

ofte

n un

iform

in s

ize.

G

row

ing

poin

t thi

n w

ith s

mal

l lea

ves

and

flow

ers

clos

e to

th

e he

ad.

PCossible auses

Mos

t ass

imila

tes

are

bein

g al

loca

ted

to th

e he

ad, l

eave

s an

d ro

ots.

O

ften

obse

rved

bef

ore

and

at fi

rst s

et.

Rel

ativ

ely

low

AD

T a

nd lo

w li

ght i

nten

sity

.

The

frui

t loa

d is

too

high

in r

elat

ion

to a

ssim

ilate

pr

oduc

tion;

ofte

n a

resu

lt of

poo

r lig

ht c

ondi

tions

. T

empe

ratu

res

are

too

high

; EC

in d

rain

and

feed

is to

o hi

gh; i

rrig

atio

n vo

lum

e is

too

low

. R

ockw

ool b

lock

is p

oorly

anc

hore

d to

the

root

ing

med

ia

indi

catin

g a

wea

k ro

ot s

yste

m.

Plant

Control Approaches

Incr

ease

AD

T b

y 1-

2o C to

hel

p us

e up

som

e of

the

exce

ss

assi

mila

tes

and

to a

ccel

erat

e flo

wer

dev

elop

men

t. In

crea

se fr

uit s

ettin

g to

tip

the

bala

nce

from

veg

etat

ive

to g

ener

ativ

e pl

ant p

arts

. T

empe

ratu

re: i

ncre

ase

spre

ad b

etw

een

day

and

nigh

t (4-

5 de

gree

s)

and

low

er n

ight

tem

pera

ture

. E

C: i

ncre

ase

abov

e 3

in r

oot z

one.

C

O2:

incr

ease

up

to 1

000

ppm

for

a sh

ort t

ime.

Ir

rigat

ion:

app

ly lo

nger

and

less

freq

uent

cyc

les.

P

rune

to 1

leaf

. A

llow

sec

onda

ry fl

ower

set

to in

crea

se fr

uit l

oad

to >

4/st

em.

VP

D: m

aint

ain

activ

e cl

imat

e at

hig

her

than

3 V

PD

.

Thi

n fr

uit

Leav

ing

2 to

3 le

aves

can

incr

ease

ass

imila

te p

rodu

ctio

n.

Tem

pera

ture

: Dec

reas

e sp

read

bet

wee

n da

y an

d ni

ght

tem

pera

ture

s. In

crea

se n

ight

tem

pera

ture

to e

nhan

ce

frui

t dev

elop

men

t and

abo

rt n

ew fl

ower

s.

EC

: Low

er E

C in

feed

and

dra

in.

CO

2: k

eep

belo

w 5

00 p

pm.

Irrig

atio

n: a

pply

sho

rter

and

mor

e fr

eque

nt c

ycle

s.

VP

D: m

aint

ain

VP

D a

t 3 a

nd h

ighe

r an

d in

crea

se R

H.

Description

Thi

ck s

tem

dia

met

er, r

elat

ivel

y lo

ng in

tern

odes

, vig

orou

s si

de-s

hoot

gr

owth

, no

frui

t set

. C

ompa

ct h

ead,

flow

ers

are

too

clos

e to

the

grow

ing

tip

(hea

d).

Sm

all l

eave

s, s

hort

inte

rnod

es, t

hin

stem

dia

met

er.

Gro

wth

is r

educ

ed o

r st

aled

.

Possible Causes

Fru

it lo

ad is

low

and

mos

t ass

imila

tes

are

bein

g us

ed to

sup

port

ve

geta

tive

grow

th.

Tem

pera

ture

: AD

T is

too

low

in r

elat

ion

to th

e lig

ht le

vels

; an

exce

ss

of a

ssim

ilate

pro

duct

ion.

D

ay a

nd n

ight

spr

ead

is to

o sm

all;

high

nig

ht te

mpe

ratu

re.

EC

: low

in fe

ed a

nd d

rain

; CO

2 –

low

; RH

– h

igh;

VP

D –

low

; M

inim

um p

ipe

– lo

w.

The

pla

nt h

as a

hig

h fr

uit l

oad

that

dra

ws

mos

t of t

he

avai

labl

e as

sim

ilate

s. D

istr

ibut

ion

of a

ssim

ilate

s to

the

head

and

roo

ts is

sig

nific

antly

red

uced

cau

sing

su

ppre

ssed

gro

wth

.

Head

Control Approaches

Incr

ease

flow

er s

et u

p to

4 fr

uit/s

tem

by

allo

win

g pr

imar

y an

d se

cond

ary

frui

t to

set.

Low

er R

H, a

void

ove

ruse

of s

cree

ns, e

spec

ially

dur

ing

clou

dy d

ays

with

low

er th

an 3

VP

D.

Incr

ease

min

imum

pip

e te

mpe

ratu

re.

Dec

reas

e te

mpe

ratu

re s

prea

d be

twee

n da

y an

d ni

ght.

Incr

ease

the

nigh

t tem

pera

ture

1o C

. T

hin

exce

ss fr

uit i

f pos

sibl

e.


2.

“R

ead

ing

th

e P

lan

t”

Tab

le 2

-1. (

Co

nt’

d)

Des

crip

tio

n, p

oss

ible

cau

ses

and

co

ntr

ol a

pp

roac

hes

fo

r u

nb

alan

ced

veg

etat

ive

and

gen

erat

ive

gro

wth

.

Str

on

gly

Veg

etat

ive

Str

on

gly

Gen

erat

ive

Description La

rge,

upr

ight

faci

ng fl

ower

. O

vary

ofte

n m

issh

apen

. F

ruit

not f

ull o

r bl

ocky

, with

2 to

3 c

ham

bers

inst

ead

of 4

cha

mbe

rs.

Wea

k an

d sm

all f

low

er b

uds

that

sta

nd u

prig

ht.

Suc

h bu

ds a

bort

bef

ore

open

ing.

S

mal

l flo

wer

(<2

.0 c

m in

dia

met

er)

with

a th

in s

tem

that

of

ten

stan

ds u

prig

ht.

PCossible auses

Larg

e, v

eget

ativ

e flo

wer

s ar

e pr

oduc

ed w

hen

ther

e is

exc

ess

of

assi

mila

tes

Low

(<1

6o C)

or h

igh

(>28

o C)

tem

pera

ture

and

low

RH

T

he u

prig

ht p

ositi

on o

r po

or a

lignm

ent o

f the

flow

er s

truc

ture

s pr

even

ts o

r re

duce

s fe

rtili

zatio

n ca

usin

g fo

rmat

ion

of s

eedl

ess

and

mis

shap

en fr

uit.

Hig

h fr

uit l

oads

may

res

tric

t ass

imila

te d

istr

ibut

ion

to

new

ly fo

rmed

flow

ers,

red

ucin

g fr

uit s

et a

nd r

estr

ictin

g ve

geta

tive

grow

th.

A c

ombi

natio

n of

hig

h A

DT

and

low

acc

umul

ated

ligh

t ca

n al

so r

educ

e fr

uit s

ettin

g an

d ve

geta

tive

grow

th.

Flowers

Control Approaches

Avo

id e

qual

day

and

nig

ht te

mpe

ratu

res

and

low

VP

D’s

that

favo

ur

exce

ssiv

e ve

geta

tive

grow

th.

Do

not l

et s

econ

dary

flow

ers

set;

they

are

low

er q

ualit

y th

an th

e pr

imar

y, m

ain

stem

flow

ers.

T

hin

seco

ndar

y fr

uit w

here

pos

sibl

e.

Red

uce

AD

T b

y 1o C

and

ens

ure

a lo

w p

re-n

ight

te

mpe

ratu

re fo

r a

few

hou

rs.

Incr

ease

CO

2 co

ncen

trat

ion

up to

100

0 pp

m fo

r se

vera

l da

ys to

impr

ove

assi

mila

te p

rodu

ctio

n of

new

flow

ers.

S

et A

DT

not

gre

ater

than

21o C

for

frui

t set

ting

at 2

00

joul

es/c

m2 /d

ay.

Diption escr

Str

ong,

wel

l-mat

ted,

whi

te r

oots

eve

nly

dist

ribut

ed th

roug

hout

the

bag.

W

eak,

poo

rly m

atte

d an

d of

f-w

hite

col

our

root

s. T

he

rock

woo

l blo

ck is

poo

rly a

ncho

red

to th

e sa

wdu

st b

ag.

Possible Causes

Str

ong

vege

tativ

e gr

owth

dur

ing

prop

agat

ion

and

durin

g fir

st fe

w

wee

ks in

a g

reen

hous

e is

crit

ical

for

esta

blis

hmen

t of a

str

ong

root

sy

stem

. G

row

th o

f roo

ts is

str

ongl

y re

duce

d at

the

begi

nnin

g of

frui

t pr

oduc

tion.

Mai

nten

ance

of a

low

frui

t loa

d du

ring

first

frui

t set

is

criti

cal f

or e

stab

lishm

ent o

f str

ong

root

s.

Poo

rly p

ropa

gate

d se

edlin

gs a

nd e

xces

sive

frui

t loa

d at

th

e fir

st s

ettin

g ca

n su

ppre

ss r

oot g

row

th.

Lack

of n

ew d

evel

opin

g w

hite

roo

ts o

r in

sev

ere

situ

atio

n,

mas

sive

roo

t die

-bac

k.

Roots

Control Approaches

Use

war

m ir

rigat

ion

(20o C

), m

inim

um p

ipe,

and

long

irrig

atio

n cy

cles

to

pro

mot

e gr

owth

and

eve

n di

strib

utio

n of

roo

ts th

roug

hout

the

med

ium

. F

ruit

load

of 1

to 1

.2 fr

uit p

er s

tem

for

early

see

ded

plan

ts w

ill

sust

ain

heal

thy

root

gro

wth

.

Pru

ning

exc

ess

frui

t will

re-

dire

ct s

ome

flow

of a

ssim

ilate

s to

roo

ts.

Mai

ntai

n op

timal

gro

wth

con

ditio

ns o

f roo

ts.


2.

“R

ead

ing

th

e P

lan

t”

Tab

le 2

-2.

Str

ess-

rela

ted

gro

wth

ab

no

rmal

itie

s

P

lan

t P

arts

S

ymp

tom

s P

oss

ible

Cau

se

Co

ntr

ol A

pp

roac

hes

Leav

es in

hea

d cu

pped

dow

nwar

d.

In

dica

tion

of w

ater

str

ess

espe

cial

ly d

urin

g ea

rly

plan

t est

ablis

hmen

t. In

res

pons

e to

exc

ess

tran

spira

tion

in r

elat

ion

to w

ater

sup

ply,

leav

es r

oll

dow

nwar

d to

red

uce

leaf

sur

face

are

a.

Hig

h te

mpe

ratu

res,

hig

h V

PD

, hig

h E

C

Pla

nt r

equi

res

mor

e irr

igat

ion.

Ens

ure

over

-dra

in is

on

targ

et a

nd c

onsi

der

a ni

ght w

ater

ing.

T

empo

raril

y re

duce

EC

. D

ecre

ase

the

VP

D a

nd C

O2

D

ull l

eave

s

Pep

pers

gro

wn

unde

r an

act

ive

clim

ate

shou

ld h

ave

shin

y le

aves

dur

ing

the

dayl

ight

hou

rs a

nd d

ull

leav

es a

t the

end

of t

he d

ay.

Dul

l lea

ves

thro

ugho

ut

the

day

can

indi

cate

: ina

dequ

ate

tem

pera

ture

re

gim

es, m

oist

ure

stre

ss, p

oor

grow

th s

peed

, too

hi

gh C

O2

leve

ls a

nd lo

w R

H.

Re-

eval

uate

tem

pera

ture

, irr

igat

ion

and

RH

reg

imes

. R

educ

eCO

2 le

vels

Bub

ble

tissu

e on

leav

es &

mar

gina

l bu

rn o

f new

leav

es.

Exc

ess

CO

2 un

der

low

ligh

t int

ensi

ty a

nd lo

w

tran

spira

tion

rate

s.

Sub

-leth

al le

vels

of b

y-pr

oduc

t com

bust

ion

gase

s su

ch a

s N

Ox

and

ethy

lene

.

Red

uce

CO

2 le

vels

to a

max

imum

700

pp

m in

ear

ly g

row

th s

tage

s.

Che

ck fo

r th

e pr

esen

ce o

f air

cont

amin

ants

.

Dar

k le

aves

.

Som

e cu

ltiva

rs, e

.g. E

agle

tend

to h

ave

dark

er g

reen

pi

gmen

tatio

n.

Pla

nts

grow

n un

der

supp

lem

enta

l lig

ht w

ill h

ave

‘b

lack

-gre

en’ a

nd p

urpl

e pi

gmen

tatio

n on

the

petio

les

and

vein

s of

the

leaf

. In

suffi

cien

t wat

er d

ue to

plu

gged

drip

pers

.

Ens

ure

drip

pers

are

wor

king

Hea

d is

dar

k in

a.m

. whe

reas

it s

houl

d ha

ve a

yel

low

ish

colo

ur th

at d

oesn

’t da

rken

bef

ore

13:0

0.

Lack

of a

ctiv

e cl

imat

e.

Sho

rtag

e of

wat

er a

t nig

ht.

Mai

ntai

n ac

tive

clim

ate

VP

D o

f 3 -

7

Ens

ure

adeq

uate

wat

er a

t nig

ht.

Tar

get 3

% o

ver-

drai

n by

third

irrig

atio

n cy

cle.

Leaves

Thi

n le

aves

esp

ecia

lly in

the

head

.

Und

er e

xten

ded

perio

ds o

f dar

k w

eath

er, p

lant

co

nsum

es m

ore

suga

r th

an it

pro

duce

s.

Low

ligh

t lev

els

and

elev

ated

AD

T a

t or

abov

e th

e co

mpe

nsat

ion

poin

t.

R

educ

e A

DT

to b

alan

ce p

hoto

synt

hesi

s an

d re

spira

tion.

Flowers

Abn

orm

ally

sha

ped

flow

ers

By-

prod

uct c

ombu

stio

n ga

s, e

thyl

ene,

can

cre

ate

abno

rmal

flow

ers

that

hav

e a

tend

ency

to a

bort

in

the

bud

stag

e.

Som

e of

the

pepp

er v

iruse

s ca

n al

ter

flow

er

deve

lopm

ent.

Red

uce

CO

2 le

vels

<10

00pp

m.

Use

a s

mal

l min

imum

ven

t to

prev

ent

accu

mul

atio

n of

con

tam

inan

ts.

Hav

e th

e bo

iler

chec

ked

for

com

bust

ion

effic

ienc

y of

<2

ppm

for

carb

on m

onox

ide.

La

b te

st fo

r po

ssib

le v

iruse

s


3.

Op

tim

izin

g t

he G

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ho

use E

nvir

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men

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Introduction

This chapter introduces principles of control foreach of the key components of the greenhouseenvironment. It illustrates how the control oflight, temperature, humidity, CO

2, nutrition and

irrigation influence the growth and developmentof the pepper plant. It also identifies the basicequipment such as rail pipes or vents used tocontrol the greenhouse environment.

LightGrowth and development of the plant arestrongly influenced by light, particularly itsintensity and duration. More than the othercomponents of the greenhouse environment,light characteristics are determined largely byseasonal or daily weather fluctuations. Lightinteracts extensively with other components ofthe greenhouse environment, and its manage-ment should be considered together with tem-perature, humidity, CO

2 and irrigation.

Terminology andMeasurements

The term “global radiation” refers to the fullspectrum of electromagnetic wavelengths from300 to 5000 nanometers (nm) emitted by thesun. The term “light” refers to a very narrowspectrum of electromagnetic radiation (400 to700 nm) with wavelengths visible to the humaneye. Interestingly, plants use the same wave-length range for photosynthesis therefore theterm “light” is used interchangeably with“radiation”.

Light intensity is measured typically by twomethods: photometric or radiometric. Thephotometric method measures light intensity in

units of illumination expressed in lux, lumens,candelas or foot-candles. These units are de-fined in terms of light sensitivity of the humaneye. Plants detect and respond to light differ-ently than the human eye and therefore photo-metric measurement is not appropriate forplants. The radiometric method measures andexpresses light intensity as radiant energy (seeTable 3-1).

Greenhouse control systems determine lightintensity by measuring the flow of radiant energyover a wide spectrum of electromagnetic waves(300 to 3000 nm). Most greenhouse controlsystems use the Kipp solarimeter to measureradiant energy in joules/sec or watts.

Until recently, measurements ofphotosynthetically active radiation (orphotoactive radiation = PAR) have been usedmostly in research. Contemporary greenhousecomputer systems are switching to PAR meas-urements as they describe most accurately theplant responses to light. PAR measures the flowof radiant energy only within 400 to 700 nm ofwaveband. An equivalent term, PPFD (seeTable 3-1), is expressed in µmol/m2/sec. ThePhytomonitorTM is an example of the equip-ment used for measuring PPFD in greenhouses.

Light duration is referred to as a sum of dailyradiation. It is measured by integrating lightintensity over time. For example, a fixed radia-tion of 500 watts/m2 during a10 hour period isequivalent to 500 x 3600 seconds/hr x 10 hrs =18,000,000 joules/m2/day X .0001cm2/m2 =1800 joules/cm2/day. Measures of PPFD andPAR are also integrated over the course of aday and expressed in their respective units on adaily basis.

3. OPTIMIZING THE

GREENHOUSE ENVIRONMENT


3.

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Variation in Light Intensity

Intensity and duration of light are affectedmainly by seasonal changes, daily fluctuationsand geographic location. Seasonal fluctuationsare the main cause of variability. For example,in Vancouver, B.C. the average light accumula-tion varies from 219 joules/cm2/day in Decem-ber to 2200 joules/cm2/day in July. The lightrequirement for pepper plants depends on thegrowth stage and the fruit load. For example,pepper seedlings (10 weeks old) require a mini-mum 150 to 200 joules/cm2/day for the firstfruit setting and a minimum 180 joules/cm2/dayfor growth and maintenance. Winter light condi-tions in south coastal B.C. generally exceed theminimum required levels for pepper growth andfruit set. The minimum level for fruit setting isnot always met at inland locations.

Mature plants carrying high fruit load (>35/m2)require more than 2200 joules/cm2/day. Theaverage light accumulation for July (2200joules/cm2/day) may not be enough to supportthe maximum fruit production.

The day-to-day variation in accumulated lightchanges with seasons and can range from 100to 1200 joules/cm2/day in the spring, 200 to

3000 joules/cm2/ day in the summer, 100to1200 joules/cm2/day in the fall, and 50 to600 joules/cm2/day in the winter. Of particu-lar importance is the daily variation in accumu-lated light in the early spring as it significantlyaffects rate of growth (growth speed), as wellas setting, ripening and quality of the pepperfruit. A wide day-to-day variation in accumu-lated light can increase the incidence of BERespecially when a low light period (180 joules/cm2/day) is followed by a high period (1200joules/cm2/day).

In south coastal B.C., accumulated light levelsare also affected by the greenhouse location.For example, in January, Abbotsford, Vancou-ver and Delta accumulate on average 293, 282and 329 joules/cm2/day, respectively. Slightlyhigher accumulated light levels in Delta, ascompared to the other locations, significantlyimprove plant growth and yield early in theseason.

Light Management

Although light is determined largely by outsideconditions there are a number of strategies thatcan enhance or reduce light intensity.

Table 3-1. Frequently used radiometric terms, definitions and units.

Term Definition Unit

Radiant energy Energy in the form of electromagnetic waves (300 to 3000 nm)

joules

Radiant flux The flow rate of radiant energy (300 to 3000 nm) joules/sec watts

Radiant flux density The number of photons intercepted by a unit area and time (300 to 3000 nm)

MJ/m2/day* watts/m2

Photosynthetic irradiance “PI” or Photosynthetically active radiation “PAR”

Radiation in the 400 to 700 nm waveband. MJ/m2/day* watts/m2

Photosynthetic photon flux density “PPFD”

Number of photons intercepted per area per time within 400 to 700 nm.

µmol/m2/sec mol/m2/day* µeinsteins/m2/sec

* - units measure light duration; the remaining units measure light intensity Note: Throughout this document, accumulated light values will be expressed as joules/cm2/day and light intensity values will be referred to as watts/m2.


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Enhancing Light LevelsIncreasing light reflectance by:

• use of white ground covers;

• selecting reflective coating for greenhousestructures.

Better Utilization of Light Through:

• optimal row orientation – for B.C., it is east-west although many growers choose northsouth orientation;

• annual cleaning of inside and outside glasssurfaces;

• adjusting plant density, spacing and pruningaccording to light intensity.

Reducing Light LevelsLight intensity above 600 watts/m2 can reducefruit quality and speed of growth.

Reduction of light strategies include:

• use of white wash or screens;

• adjustment of stem densities and pruningaccording to light intensity.

TemperatureThe optimum growing temperature for thepepper plant changes with plant age, light, CO

2

concentration and predominant physiologicalstage – sugar production or consumption. It isbeyond the scope of this guide to providespecific temperature recommendations. Generalprinciples of temperature control including theapplication of average daily (24 hours) tem-perature; and management of pre-night, night,and pre-dawn temperatures will be covered.

Concept of Average Daily (24hours) Temperature (ADT)

The ADT range for optimum greenhousepepper production is relatively narrow andvaries typically from 15 to 25o C. Within thisrange, the development rate of the pepper plantis directly related to the ADT and is independ-ent of day/night fluctuations.

Development of the pepper plant can remainon target even if the ADT strays outside the

range for a few days. For example, lower ADTin days one and two of –1oC and –1.5oC re-spectively can be compensated by an increasedADT in days three and four of +1oC and+1.5oC respectively. This allows pepper grow-ers flexibility in controlling overall developmentthrough temperature. The maximum period forpepper temperature compensation can’t exceed5 to 7 days. See Table 3-2 for ADT calculation.

Distribution of TemperatureOver 24 Hours

Light intensity and duration are the key factorsdetermining the optimum ADT for the pepperplant. Temperature control is therefore definedby seasonal and daily variations in light. Thecontrol of temperature during the 24 hourperiod is divided into the pre-day, boost (orday) and pre-night periods. Computer programscan be used to optimize energy and plantgrowth condition by “re-shaping” the distribu-tion of temperatures over the 24 hours.

During winter (short day/long night), whenheating is used without venting, temperature isoptimized during daylight and reduced moder-ately during the night. This control strategyresults in a small temperature difference betweenday and night (see Figure 3-1). In the summer(long day/short night), when both heating andventing are used, the length and degree-drop inthe night temperature are key managementstrategies for controlling the ADT. Summercontrol strategy results in a large temperaturedifference between day and night as the daytimetemperature often exceeds its daytime set point.

Table 3-2. ADT calculation (average daily temperature).

Time Block (24 hr clock)

Hours in

Block

Setting in C

Hour Degrees

9 to 11 2 18 36

11 to 16 5 22 110

16 to 23 7 16 112

23 to 9 10 18 180

438 24 = 18.25 C


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Pre-day (Fig 3-1, A)The rate of temperature increase during thepre-day period is proportional to the lightintensity of the previous day. It should not,however, exceed 1oC /hr or it can negativelyaffect fruit quality and could pose a risk of dewpoint formation or stem wetness.

During sunrise, the contribution of the railpipes to the overall temperature control de-creases as the contribution of sun radiationincreases. The transition point is at 200-300watts/m2.

Boost or Day (Fig 3-1, B)The term “boost” is used to describe an in-crease in temperature during mid-day or thebrightest part of the day. The boost is typicallyapplied during the winter, spring and fall toincrease the temperature difference betweenthe day and night. The temperature increaseand the duration of the boost are proportionalto the light intensity and plant vigour.

Pre-night (Fig 3-1, C)The length of the pre-night extends with anincrease in the day length. The rate of tempera-ture decrease during pre-night depends on outsidetemperatures. It is typically low during summerand increases during winter, spring and fall.

Influence ofTemperature Controlon Pepper Growth

Effect of Temperature onVegetative or GenerativeGrowth

A “balanced plant” produces enoughassimilates to support vegetative andgenerative growth regardless of weatherconditions. Plant balance is accomplishedby continuously adjusting temperature inrelation to light intensity. Table 3-3 illus-trates general principles used to correctpepper growth by adjusting temperatureunder different light conditions.

Effect of Temperature on FruitDevelopment and Quality

The first fruits set have a tendency to be ‘flat’in shape. Introduction of a short pre-nighttemperature of 3 to 4oC below the averagetemperature can lengthen the fruit. Maintainingrelatively low day temperatures improves fruitfirmness and shelf life.

Effect of Temperature onPartitioning of Assimilates

Demand for assimilates can be influenced in partby temperature differences between plant tissues.These can be manipulated to enhance the flowof assimilates. For example, dropping the tem-perature quickly at sunset will cause pepperfruits and roots to retain higher temperatureslonger than other plant parts. This will direct theflow of assimilates to the fruit and roots. Theincrease of assimilate flow will be proportionalto the differential temperature between tissuesand the rate of the temperature drop.

Figure 3-1. The average daily temperature (ADT) of 20.5o C:

differences in temperature distribution between spring and

early summer. The same principles apply to operations having

four growing periods.


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Equipment for

Temperature Control

Rail PipeThe rail pipe is the primary heating unit in thegreenhouse controlling:

• temperature, use of the rail pipe for tempera-ture control is largely defined by outsideweather conditions and ADT targets;

• RH within the canopy; and

• plant activation, i.e. to stimulate the plant totranspire, use is limited to specific day hoursor weather conditions. Figures 3-2a and 3-2billustrate how the rail pipe can be used tohelp activate the plant.

Example 1: Minimum pipe temperatures

(40 to 50oC)

The example illustrates the use of a minimumrail pipe during a cloudy summer day (>15oC).It is used for a short time in the morning untilthe sun’s radiation reaches a minimum 300watts/m2.

Example 2: Maximum pipe (>50oC)

The example illustrates the use of a maximumrail pipe during a very cold (< 8oC) but sunnywinter or spring day. It is used for plant activa-tion in the morning and during the “boost”period for 2 to 3 hours.

Grow PipeA grow pipe is used to supplement rail pipeheat mostly during the initial establishmentphase. It provides more uniform climate withina canopy. It is sometimes used to distribute theheat by-product from CO2 production. Benefitsof using the grow pipe include:

Table 3-3. Control of pepper “balance” in relation to temperature and light intensity.

Light High

Average Daily Temperature (ADT)Low

Average Daily Temperature (ADT) Low Light

Early winter late fall Growth tendency: too generative Control: - Decrease ADT; - Provide a smaller spread

between day and night temperatures;

- Night to day transition [slow and early (max 1oC/hr)];

- Day to night transition [slow (1 – 2oC/hr)].

Winter, fall and overcast days Growth tendency: too vegetative Control: - Increase ADT; - Provide a larger spread

between day and night temperatures. Heating increase on light and include boost.

- Night to day transition [rapid and late (1 – 2oC/hr)];

- Day to night transition [rapid (1- 4oC/hr)].

High Light

Late spring, summer and early fall Growth tendency: too generative Control: - Decrease ADT; - Provide a smaller spread


- Decrease the pipe heat based on light;

- Night to day transition [slow and early (1oC/hr)].

Early spring late fall Growth tendency: too vegetative Control: - Increase ADT; - Provide a larger spread


- Increase pipe heat based on light;

- Night to day transition [rapid and late (1 – 2oC);]

- Day to night transition [rapid (4oC/hr)].


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• better control of root temperature in therooting phase and during 1st flowering stage;

• better maintenance of optimum ‘head’temperatures during venting when outsidetemp < 12oC; and

• improved control of pathogens.

Venting

Vents are used to control the ADT and humid-ity by removing excess heat and moisture fromthe greenhouse. Temperature control is accom-

plished by using the following methodsand concepts: percentage of vent open-ing, ‘P band’ and ‘dead zone’, and theapplication of the lee or wind side vents.Note that some computer control sys-tems use different control settings.Consult each computer system forspecific information relating to ventila-tion control.

Dead Zone is a term used to indicatethe difference between the heat set pointand venting set point. In the early springand late fall when outside temperaturesare less than 8oC this difference is 2 to3oC and during summer or at tempera-ture higher than 15oC it decreases to 0.5to1oC.

P Band refers to the range of tempera-tures over which vents open.

The speed of opening and closing thevent is determined by P band range. Aslow-acting P band (large temperaturerange) with a large dead zone, is used inearly spring and late fall when outsidetemperatures are less than 8oC. A fastacting P band (small temperature range)with a small dead zone, is used when thetemperature is higher than15oC (seeTable 3-4).

A combination of slow acting P band and largedead zone restricts the duration and frequencyof venting and ensures slow and restrictedopenings to prevent cold air chilling the plantheads. In contrast, a combination of fast acting Pband and small dead zone assures almost con-tinual venting and faster opening and closing ofvents, to react to summer weather conditions.

Adapted from presentation by Vortus, 2000

Figure 3-2a. Plant activation with minimum

pipe temperature

Figure 3-2b. Plant activation with maximum

pipe temperature


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The use of lee and wind side vents is deter-mined by both the seasonal weather pattern andby the speed and direction of the wind. Duringthe spring, venting begins with opening the leeside only. The wind side is closed to preventcool air (8 – 15oC) from blowing directly on theplant heads. The opening created by the leevent draws air from the greenhouse. The windside vent is opened only when the outsidetemperatures are higher than 15oC and windspeed is lower than 2 m/sec. In the summermonths, the wind side is used more actively.

Moveable and Fixed Screens

Moveable and fixed screens are used temporar-ily (4 to 6 weeks) during plant establishment tosave energy and enhance greenhouse climate.Screens provide a more uniform temperaturedistribution throughout the greenhouse andoptimize VPD when outside temperature ishigher than 8oC. The use of screens lowerspipe temperature to below 65oC, preventingbuild up of root pressure.

Fixed screens are made of polyester withseveral pin size holes spaced 20 x 20 cm or 10 x10 cm/m2. This allows slight ventilation whenVPD is lower than 3 and prevents cold air fromreaching the plant heads. Some screens have amanual system to allow partial opening andclosing. Overuse of screens can cause stretchedsoft growth, which is more susceptible todiseases, and may also reduce growth speed.

Moveable screens are also used to reduce lightintensity (>700 watts/m2) in transition and hotweather. This improves fruit quality and con-trols growth speed.

Whitewash, fog and roofsprinklers

Whitewash, fog and roof sprinklers are used toreduce plant stress and prevent fruit sun-scaldby lowering the inside air temperature by 1 –3oC. They are used when the outside or insidetemperature exceeds 26oC, RH is lower than60% or VPD is higher than 10.

Whitewash reflects solar radiation, reducingthe amount of energy entering a greenhouse.Whitewash as liquid “chalk” is applied throughthe roof sprinklers at 30 to 124 kg/ha. De-pending on the application rate, whitewash canprovide varying degrees of reflection.

Fog (water droplets smaller than 35 micronsdispersed at 1000 psi inside the greenhouse)and roof sprinklers are used to reduce airtemperature by 1 to 2.5oC and elevate RH.Both are activated during transitional weatheror during hot spells. Fog should be discontinuedin time to allow the crop to dry off before nightto prevent pathogen infection.

Table 3-4. Summary of seasonal venting strategies used for temperature control

General Venting Seasonal Strategies

Outside temperature

Vent opening

(%) Lee vent

Wind side vent P band Dead zone

winter <8oC 0 – 2 yes -- slow acting large 2 – 5oc

spring <8 – 12oC

1 – 20 yes, start at 300 watts

yes, if wind <2 m/sec slow acting large

2 – 3oc summer >15oC

1 – 100 yes, start at 300 watts yes fast acting small

0.1 – 1.0oc fall <8 – 12oC 1 – 100 yes, start at

300 watts yes, if wind <2 m/sec slow acting large

2 – 3oc


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Humidity

Terminology

The term “humidity” refers to the water vapourconcentration in the air at a given temperature.The amount of water vapour the air can holdincreases with temperature. For example, at13.9oC, air can hold a maximum of 12 g/m3.Condensation will occur if the air temperaturecools below 13.9oC. The temperature at whichcondensation occurs is called the dew point.Within the temperature range used for pepperproduction (15 to 25oC), the maximum watercontent of air increases about 1.0 gram per m3

for each 1°C rise in temperature.

In commercial operations, humidity control isprimarily concerned with encouraging planttranspiration to maintain an “active climate”while preventing condensation on the planttissue (dew point). Management of both relieson measurement of water vapour content in theair which can be expressed as a weight (ormass) of water vapour per volume of air (g/m3

or kg/m3) or as a pressure exerted by watervapour in the air expressed in pascals or milli-bars (see Table 3-5).

Measurements of RH, VPDand MDLA

The value of RH or VPD is calculated from themeasurements of temperature and water vapourconcentration of the air. Calculation of theMDLA value requires measurement of the leaftissue temperature. In commercial operations, airtemperature and humidity are measured with awet and dry psychrometer, hygrometer or capaci-tive meter. Embedded thermistors or infraredthermometers measure leaf temperature.

Role of RH, VPD and MDLA inManaging an Active Climate

A primary concern in controlling greenhousehumidity is the establishment of an activeclimate that stimulates plants to transpire. Thekey driving force of transpiration is the differ-ence in water vapour concentration betweenthe leaf stomata and the greenhouse air. Thefollowing paragraphs discuss importance of theRH, VPD and MDLA values in management ofan active climate.

Relative Humidity (RH) RH measuresthe degree of air saturation by calculating the

Table 3-5. Common water vapour terms and units used in greenhouse industry.

Term Definition Unit Absolute humidity Concentration of water vapour per unit volume of air.

g/m3, kg/m3

Dew point (Tdp) The temperature to which air must be cooled to produce condensation.

oC

Relative humidity (RH)

Measures degree of air saturation with moisture by calculating a ratio between the actual and saturated water vapour concentration for a given temperature of air. RH = actual water vapour concentration x 100% saturated water vapour concentration

%

Moisture deficit or vapour pressure deficit (VPD)

Difference between the water vapour pressure (or vapour density) at the saturation point and the actual pressure (or density) at the same air temperature. VPD = saturated vapour pressure of air – actual vapour pressure of air

kPa, millibar g/m3*

Moisture deficit leaf-air (MDLA)

Difference between the water vapour pressure (or density) in the leaf stomata and the water vapour pressure (or density) in greenhouse air. MDLA= saturated water vapour pressure of stomata – actual water vapour pressure of air

g/m3

millibar

*Throughout this guide, the value of VPD is presented in g/m3 unit.


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ratio (%) of actual water vapour concentrationto saturated water vapour concentration at anygiven temperature. The RH value does notchange predictably in response to a change intemperature or concentration of water vapour.The RH value is not a good indicator for man-agement of the active climate.

Vapour Pressure Deficit (VPD) VPD isa more sensitive indicator of the water vapourconditions than RH. It measures the differencein concentration of water vapour betweensaturated air and greenhouse air at the sametemperature. The VPD value always changes indirect response to a change in temperature orwater vapour concentration. Changes in VPDare always followed by changes in the transpira-tion rate; VPD is a much better indicator thanRH for the management of an active climate.

Moisture Deficit Leaf to Air (MDLA)MDLA measures differences in concentrationof the water vapour between the leaf stomataand the greenhouse air. It is the most sensitiveindicator of the transpiration rate and growersshould rely on its values for management of anactive climate.

Role of RH and VPD inManagement of Condensation(Dew Point)

Avoiding condensation on plant tissue is equallyimportant to the management of an activeclimate. Disease prevention and fruit qualityassurance rely on effective humidity manage-ment. Condensation on plant tissue depends onthe extent of air saturation and the temperaturedifference between the greenhouse air and theplant tissue. Condensation occurs when thewater vapour in the air or surface of the planttissue is cooled down below the dew point. Asthe RH of air increases, the temperature dropthat will trigger condensation decreases, creatinga risk of condensation (see Table 3-6). Thetemperature difference required to cause conden-sation depends only on degree of air saturationwith moisture and is independent of the tem-perature of the greenhouse air (seeTable 3-7).

In contrast to the management of an activeclimate, RH is a very good indicator for man-agement of the dew point. The RH valueshould always be considered in climate controldecisions designed to control condensation,disease pathogens, and fruit quality. VPD canalso be used to predict condensation. There isa range of VPD values, defined by changingtemperature, for each RH level and degree (oC)drop in temperature (see Table 3-7).

Control of Humidity

Removing Humidity fromGreenhouse Air

Humidity of greenhouse air depends on tem-perature, degree of condensation, and ventila-tion. Ventilation and condensation reduceshumidity in the air whereas changes in tempera-ture affect the capacity of air to hold watervapour without affecting its absolute watervapour content.

Water vapour diffuses from areas of higher tolower concentration. For example, greenhouseair is usually more humid than outside air dueto crop transpiration. The concentration differ-ence between the greenhouse and outsidehumidity drives the humid air outside throughopened vents. Similarly, temperature differencesbetween the inside and outside of the green-house act as a driving force for water vapourexchange. The rate of water vapour removal isdetermined by the magnitude of this difference(i.e. the larger the difference, the more watervapour is removed).

During winter, spring, and fall, the temperatureof the glass or plastic screen surface is typicallya few degrees cooler than temperature of thegreenhouse air, causing condensation on itssurface. The extent of condensation is deter-mined by the humidity level in the greenhouseair and temperature differences between thegreenhouse air and the glass.


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Seasonal Changes AffectingControl of Humidity

The need for humidity control is largely deter-mined by seasonal changes in outside tempera-ture, RH, wind speed and wind origin, as well asseasonal variation in canopy transpiration rates.

In winter, plants generate a relatively smallamount of water vapour (1.0 L/m2) per day,reducing the need for humidity control. Therate of transpiration increases during the spring(1.5 L/m2/day) and summer (3.0 L/m2/day)increasing the need for humidity control (seeFigure 3-3).

Temperature and RHThe amount of vent opening is determined bydifferences in both temperature and watercontent between the greenhouse and outsideair. The water vapour content of the outside airis at the lowest value in late January, early

February and at the highest in September. Inwinter and early spring, differences in tempera-ture and RH between the greenhouse andoutside air are the highest and therefore only asmall (1 to 4%) vent opening is needed to lowerthe overall vapour pressure in the greenhouse.In the fall, inside and outside air temperaturesare similar, and a larger vent opening (>20%) isrequired to remove water vapour.

Air OriginThe percentage of water vapour concentrationin outdoor air is also related to the origin of air.In B.C., continental air from the east (Interior) isusually dry and contains little water vapour;whereas marine air from the west has a higherwater vapour percentage. The origin of the airaffects the choice of the vent side and thepercentage of vent opening. A predominance ofcontinental air calls for a small vent opening onthe lee side whereas marine air requires a largervent opening using both lee and wind sides.

Table 3-6. The relationship between RH and temperature drop or differences that will cause condensation (dew point).

Temperature of the

greenhouse air RH values

16 to 22 oC 80% 85% 90% 95% Required temperature

difference between air and a surface that will cause

condensation (dew point )

3.5oC

2.5oC

1.6oC

0.8oC

Table 3-7. The relationship between VPD and temperature drop or differences causing condensation (dew point).

Temperature of the greenhouse air VPD (g/m3) at following RH values

oC 80% 85% 90% 95% 16 2.7 2.0 1.3 0.7 17 2.9 2.2 1.4 0.7 18 3.1 2.3 1.5 0.8 19 3.3 2.5 1.6 0.8 20 3.5 2.6 1.7 0.9 21 3.7 2.8 1.9 1.0 22 3.9 2.9 1.9 1.0

Required temperature difference between air and

a surface that will cause condensation (dew point )

3.5oC

2.5oC

1.6oC

0.8oC


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Wind SpeedThe rate of water vapour removal (g/m2/hr) fromthe greenhouse increases with wind speed. Windspeed affects the choice of vent opening (lee orwind side). In general, at wind speed higher than 2m/sec, ventilation is restricted to the lee side only;whereas at wind speed lower than 2 m/sec, bothlee and wind sides can be used (see Table 3-8).

Daily ChangesAffecting ControlStrategies

Although less variable than sea-sonal changes, the humidity levelsof the outside and greenhouse airfluctuate over a 24-hour period.The lowest humidity of outside airis observed at sunrise and thehighest in the early afternoon dueto increased transpiration. Humid-ity inside the greenhouse dependson the degree of venting and istypically at the lowest level at mid-day and highest before sunset.Optimum daily humidity is main-tained using heat and ventilation.

Exact applications of both depend on the seasonand time of the day (see Table 3-9).

Figure 3-3. Seasonal humidity control by condensation and

ventilation without the use of screens

2.5

2.0L/m2/day

1.5

1.0

.5

winter spring summer fall

Condensation Ventilation

Table 3-8. Effects of seasonal climate conditions on methods of humidity control.

Methods of humidity control Outside air conditions affecting control decisions

Venting Seasons

Main Method

Opening %

Lee or

wind

Temp. oC

Water vapour

g/m3

Wind speed m/sec

Origin of air

winter

condensation

<1

lee <8 5.0

high >2

continental

spring condensation, venting, screening

<10 lee <12 6.0

moderate

<2 marine

summer

mainly venting, condensation, fog, screening, roof sprinklers

>50 lee and wind >15 11.8

moderate

<2

marine

fall venting, condensation

>20 lee and wind

<12 10.0 moderate

<2 marine


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Control strategies:

• Combine gradual temperature ramping (1oC/hr) with a minimum vent to maintain RHbelow 85%;

• Ensure that the plant temperatures are atdaytime targets prior to sunrise.

Preventing Condensation Dueto Radiation Loss

During clear, cold nights (winter, spring andfall) the top of the plant canopy can lose heatdue to radiation loss. The cool plant surfacescombined with the high humidity of the green-house air can result in condensation on theupper plant canopy.

Control strategies:

• Under clear, cold night conditions set aver-age night time temperatures above the target;

• Ensure uniform tissue temperatures through-out the canopy by raising the temperatureand humidity sensors closer to the upperplant height especially when the crop hasreached the wire;

• Use screen to improve the uniformity oftissue temperature; and

• Provide minimum venting to ensure RH levelis below 85%.

Avoiding Condensation

– Dew PointIn commercial operations, condensation on planttissue may occur during the night-to-morningtemperature transition (plant activation), onclear and cold nights (radiation loss from theplant tissue) and during venting when outsidetemperature is below 8°C (aggressive venting).Uneven distribution of humidity or temperaturewithin a greenhouse or among plant tissues canincrease the risk of condensation.

Preventing CondensationDuring Plant Activation

The temperature of greenhouse air increases ata faster rate than the temperature of planttissues. The larger the tissue mass; the slower towarm up, e.g. leaves will warm up faster thanstems or fruit. The process of ramping uptemperature from night to morning can create atemperature difference among different tissueswithin the canopy. This happens when airtemperature is increased faster than 1oC/hr.The risk of condensation becomes higher whenthe morning sun raises air temperature at anaccelerated rate (e.g. 5oC/hr).

Table 3-9. General principles of applying heat and ventilation for the control of seasonal and daily variations in humidity.

24-hour Control Strategies (pipe temp in oC; vent opening in %)

Seasons Night Pre-dawn Sunrise Mid-day Late afternoon Sunset

Pre-night

winter pipe>50o pipe >50o pipe >50o pipe >50o pipe >50o pipe >50o pipe <40o

spring pipe>50o pipe>50o

vent<10 lee side

pipe 40o

vent <10 lee side

pipe <40o

vent<10 lee side

pipe <40o

pipe< 40o

pipe <40o

summer

pipe<40o pipe >50o

vent <10 lee & wind

pipe 40o

vent >20 lee & wind

pipe <40o

vent >50 lee & wind

pipe <40o

vent >30 lee & reduced wind

pipe<40o

vent>50 lee & wind

pipe<40o

vent >20 lee & wind

fall

pipe<40o pipe >50o

vent <10 lee side

pipe >40o

vent >20 lee & wind

pipe >40o

vent >20 lee & wind

pipe >40o

vent <10 lee & wind

pipe >40o pipe <40o


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Distribution of Humidity andTemperatures

Temperature and RH are monitored continu-ously in commercial greenhouses but under-standing a greenhouse microclimate depends ongrower awareness. There are several considera-tions impacting the distribution of humidityand temperature within a greenhouse and theplant canopy:

• Variable temperature distribution within agreenhouse may be related to the age of thegreenhouse, its design and orientation oreffectiveness of the heating system;

• Inconsistent horizontal or vertical distribu-tion of humidity within a greenhouse andplant canopy;

• Seasonal temperature differences betweenthe greenhouse air and plant tissue;

• Inherent property of the transpiring tissue:i.e. during active transpiration the boundarylayer of leaves has about 10% higher humid-ity than the surrounding air.

Carbon Dioxide

Introduction

CO2 enrichment is a standard practice in com-

mercial operations to enhance yield. Researchand commercial CO

2 enrichments have demon-

strated yield increases of 20 - 40%. In additionto overall growth enhancement, high CO

2

concentrations are also used to stimulate flowerinitiation and fruit development.

The effectiveness of CO2 enrichment depends

on leaf area, light intensity, CO2 concentration,

duration of dosing, source of CO2, and the

design and calibration of the delivery system.This chapter discusses strategies for CO

2

enrichment as they relate to light intensity,degree of ventilation and costs. It also intro-duces the common greenhouse air pollutantsand discusses their effects on pepper growth.

Sources of CO2

Most commercial greenhouses burn natural gasin a boiler. Recovered flue gases can be used forCO

2 enrichment. Food grade liquid CO

2 is also

used, primarily during early stage of peppergrowth as young pepper plants are most sensi-tive to trace impurities in flue gases. LiquidCO

2 is the safest source of carbon dioxide as it

is practically free of impurities but it is themore expensive source.

Combustion of 1 m3 of natural gas with 8.5 m3

of air produces 10 m3 of flue gases of which 1.8kg is CO

2. Other fuel sources such as propane

can be burned to generate CO2-rich flue gases.

For example, combustion of 1 liter of propaneproduces 5.2 kg of CO

2.

Measuring CO2 Applications

There are essentially two measurements used ingreenhouse vegetable production for dosing ofCO

2: (1) rate of CO

2 application, expressed in

kg/ha/hr, and (2) the amount (m3) of naturalgas burned per m2 per unit time, assuming 1.8kg of CO

2 per 1m3 of natural gas burned.

Information collected in the past few yearsindicates that average gas combustion amountsto 65m3/m2/ year with an average CO

2 applica-

tion of 108kg/m2/year. The amount of CO2

applied for pepper production ranges typicallyfrom 25 to 70 kg/hr/1000 m2. A full canopycrop under bright light conditions requires 50kgCO

2/hr/ha to maintain ambient levels.

The “set point application” is measured in partsper million (ppm). CO

2 sensors monitor con-

tinuously the concentration of CO2 in the

greenhouse air and call for application when theconcentration of CO

2 falls below the target.

The ppm values are often set above the targetto ensure that application rates are alwaysabove the ambient level, especially under fullsummer venting. Values of CO

2 (ppm) are used

to control ventilation in the night as well asduring the day.


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is the primary strategy for optimization ofCO

2 uptake and enhancement of plant

growth.

• Under high light intensity (late spring and sum-mer), concentrations of CO

2 in the greenhouse

air can be reduced to economically acceptablelevels (350 to 500 ppm), and the pepper plantswill continue to produce enough assimilates tosupport heavy fruit load and growth.

Seasonal and DailyStrategies for CO

2

EnrichmentSeasonal and daily fluctuations in light intensityand the degree of ventilation are the two mainfactors that define application rates of CO

2 in

commercial pepper operations.

During winter and early spring, when lightduration and intensity is low, CO

2 application

rates can reach 1000 to 1200 ppm with liquidgas and up to 1000 ppm with flue gases. Al-though CO

2 set points are high, the proportion

of gas allocated to CO2 enrichment in the

winter is relatively low as compared to theheating needs. This is due in part to the lack ofventilation and low CO

2 uptake. In south

coastal B.C., applications of CO2 in weeks 52

through 9 average only 0.2kg/m2/week.

During late spring and summer,when light intensity is high,ventilation and cost of CO

2

become the two primary factorsdetermining application rates.During this period, concentrationsof CO

2 in the greenhouse air are

typically maintained at 350 to 500ppm. Application rates of CO

2

increase 5-fold as compared towinter to an average 1.0 kg/m2/week (weeks 9 to 45). This is dueto greater ventilation losses andincreased CO

2 uptake by the

mature plant canopy.

Principles of CO2 Control

The optimum application rates of CO2 are

defined primarily by light intensity, degree ofventilation, cost of CO

2 and crop demand.

Providing there are no other limitations, therate of uptake is influenced primarily by thelight intensity and the amount of CO

2 present

in the surrounding air (see Figure 3-4).

The rate of CO2 uptake increases markedly

with an increase in light intensity, even at lowCO

2 concentrations (i.e. 200 ppm). Rate of

assimilate production and plant growth issignificantly affected by seasonal and dailychanges in light intensity. The benefit of CO

2

enrichment is particularly apparent when highCO

2 levels interact with high light intensities.

The relationship between light intensity andCO

2 concentration has important and practical

implications for commercial growers:

• Without enrichment, the level of CO2 in the

greenhouse air quickly depletes to belowambient (<350 ppm) levels. Depletion ofCO

2 in greenhouse air is a limiting factor for

plant growth.

• Under low light intensity (winter and earlyspring), maintaining a high CO

2 concentra-

tion (700 to 1000 ppm) in the greenhouse air

Figure 3-4. Influence of CO2 concentration in the air on plant uptake.

0

2

4

6

8

10

200 340 1000

Concentration of CO2 (ppm)

CO

2 U

pta

ke (

g/m

2 /hr)

400 w/m

100 w/m

20 w/m


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Uptake of CO2 takes place only in the presence

of light, therefore CO2 applications should begin

1 - 2 hours after sunrise and stop before sunset.These start and stop times will be partly influ-enced by the amount of venting and screen use.For example, under high light intensity and fullventing, CO

2 would be stopped at sunset;

whereas, on a dull day with restricted ventingand screen use, the CO

2 may be stopped 1 - 2

hours before sunset to allow plants to utilize theremaining CO

2 in the greenhouse. Table 3-10

summarizes strategies for CO2 applications.

Table 3-10. Application rates and computer set points for CO2 as

related to seasonal and daily weather variations.

Vent Opening (%) and Target CO2 (ppm) Application kg/ha/day Dawn Mid-morning Mid-day Late afternoon Dusk

winter 15-20*

0 % 700 ppm

0 700

0 700

0.1 <500

CO2 shut off

0 <500

CO2 shut off spring

120-150

1 1000

5-10 1000

10 700

< 5 1000

<1 <500

CO2 shut off summer

200 1-5

1000

10 500

100 400

<100 500

<50 700

fall 120-150

1 1000

5-10 1000

10+ 700

< 5 1000

<1 <500

CO2 shut off * Application rates and CO2 targets presented in this table are average as opposed to specific recommendations and will vary with each individual greenhouse.

Table 3-11. General rule for estimating the % yield increase at different CO2 concentrations and light levels

Yield increase (%) per 100 ppm increase in CO2

CO2 increment

1.2 (low light) 1.5 (normal light) 1.8 (high light)

200 – 300 30.0 37.5 45.0 300 – 400 13.3 16.7 20.0 400 – 500 7.5 9.4 11.3 500 – 600 4.8 6.0 7.2 600 – 700 3.3 4.2 5.0 700 – 800 2.4 3.1 3.7 800 – 900 1.9 2.3 2.8 900 – 1000 1.5 1.9 2.2

1000 – 1100 1.2 1.5 1.8 1100 – 1200 1.0 1.2 1.5

Adapted from: Groenten & Fruit Oct.94

Economics of CO2 Enrichment

The benefits of CO2 enrichment are limited

primarily by light intensity during winter and bythe degree of ventilation during summer. Use ofhigh CO

2 concentrations during winter is very

cost-effective as little is lost through ventilation.

During late spring and summer, ventilationincreases. In this situation, the strategy for CO

2

enrichment is based on a compromise betweenthe need for ventilation, cost of CO

2 and

expected net returns. Table 3-11 illustrates theexpected yield increase as influenced by CO

2

concentration at three levels of light intensity.


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Although there are obvious benefits frommaintaining CO

2 levels between 300 to 500

ppm during summer, maintaining higher con-centrations may not be cost effective. Eco-nomical levels of enrichment can be deter-mined by comparing profit due to increasedyield with the additional cost of CO

2.

Estimated yield increase can be calculated formthe following equation:

(% yield increase) y =(1000/ppmCO

2 )2 x light factor (1.2, 1.5 or 1.8)

Past experience of B.C. growers indicates thatCO

2 concentration between 320 to 500 ppm

during summer provides cost-effective returns.

Design and Calibration of CO2

Delivery System

In the case of combustion-generated CO2, flue

gases extracted by centrifugal fans are mixedwith air and cooled below 65oC. They are thenblown into a transport duct and distributedwithin the crop through poly-tubes. The distri-bution system requires a fan with adequatecapacity, a header delivery system (15-20 cmPVC) and 50 mm diameter poly-tubes.

Fan capacity can be estimated using a manom-eter, a U-shaped plastic tube mounted on aboard and filled with water. Adequate fancapacity will create 7 cm of pressure measuredat the start of the main distribution line and 4cm of pressure measured at the end of thepoly-tube line.

Design of the header system should minimizeelbow pipes as they reduce gas pressure. If thePVC header transport lines are buried, ensureadequate pipe thickness to prevent collapse orcracks and proper water-proofing with draintraps to prevent condensation from restrictingthe CO

2 flow.

The distribution poly-tubes for CO2 should

have two holes (1 mm diameter) spaced 20-30cm apart. Distance between the pores shouldincrease with the length of the tube to ensure

even distribution. Pores should be positionedon the underside of the tube. Ensure that theconnections with the supply line are sealed andthe tube ends are well knotted. This will pre-vent bending and twisting and ensure that thetubes are stretched tight to prevent accumula-tion of condensation water.

Position one poly-tube per row approximately75 cm below the plant head. Trials have dem-onstrated that CO

2 concentration within the

canopy is increased by 20 to 25 ppm whentubes are positioned 75 cm from the top of thecanopy as compared to tubes lying on theground. The rate of CO

2 uptake is highest in

the middle to upper section of the canopy.

Sensor Calibration

Concentration of CO2 in commercial green-

houses is usually measured with an infrared gasanalyzer (IRGA). Although very accurate,IRGA sensors tend to fluctuate with humidityor temperature and therefore should be cali-brated every three months.

There are different methods for calibrating theCO

2 meter. The simplest approach is to moni-

tor CO2 night readings from the computer

graphs. Under full venting the reading should bebetween 320 ppm and 360 ppm. Reading belowor above these values indicate the need forcalibration of the CO

2 meter.

The IRGA sensors can be calibrated using CO2

standards (0 to 400 ppm range for summer and0 to 1000 ppm range for winter). Measure thetime span between the application of standardsand computer response. It should be less than90 seconds, ideally 30 seconds over a distanceof 100 meters. Response time of the sensorscan be tested visually by measuring time re-quired to pull smoke through the sensor tubes.If it takes more than 90 seconds, CO

2 applica-

tion will ‘over shoot’ the computer target setpoint. Diluting the CO

2 gases with extra air can

prevent exceeding the set point target.

In addition to sensor calibration, ensure thatthe suction hose for CO

2 sensors is clean and


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free of cuts or holes. This can be checked withan air compressor. The suction hose should beplaced below the screen and protected fromfreezing or water vapour condensation.

Inaccurate sensor operation can lead to exces-sive CO

2 concentrations and plant damage.

This is of particular concern in new green-houses that tend to be tightly sealed allowingdamaging levels of CO

2 to accumulate quickly.

Concentration of CO2 in the greenhouse can

remain high or uneven despite well functioningsensors. This can be due to leakage or blockageof distribution tubes (poly-tubes). Occasionallythe spacing, number, or diameter of holes on thepoly-tubes may be outside of specification. Aportable CO

2 sensor can be used to identify

areas with excessive CO2 concentration.

Using Heat Storage toOptimize Use of CO

2

Heat storage tanks collect extra heat from theboilers during the day and release it during night.This provides more CO

2 from flue gases for

enrichment throughout the day. The capacity ofthe heat buffer tank should be designed to meetthe heating demand of a spring night. Optimumheat buffer capacity is approximately 100 m3/ha.Depending on the storage capacity, 115 - 850 m3

of natural gas can be burned/ha/day.

Heat storage saves about 13% energy. Growersusing heat storage consume similar amounts ofgas as growers without heat storage but in-crease their CO

2 dose by one third. The effi-

ciency of heat storage is highest with a CO2

requirement of 340-400 ppm.

Air Pollutants

Sources of Air Pollution

Peppers are very sensitive to by-product gasesfrom incomplete natural gas combustion,exhaust from propane forklifts, and weldingoperations. They are also sensitive to naturalgas escaping from pipe joints and pollutantsreleased from PVC pipes heated above 65oC.

Vapours released from new PVC materials andcontaminants included in non-food grade CO

2

can also reach damaging levels, especially underrestricted ventilation. Paint, clean-up chemi-cals and pesticides on heat pipes may be vola-tilized. Any or all of these pollutants cannegatively affect pepper growth.

Common Pollutants

The most common air pollutants associatedwith incomplete combustion include ethylene(C2H4), oxides of nitrogen (N

2O and NO

2,

collectively referred to as NOx), sulphur diox-ide (SO

2), ozone (O

3), carbon monoxide (CO)

and hydrogen sulphide (H2S). Preventing air

pollutants from being formed depends onmaintaining optimum combustion conditions.Multi-stage emission control systems thenprevent pollutants from leaving the flue.

Ethylene (C2H4)

Ethylene gas is produced as a result of incom-plete combustion. It can also be found in flueand vehicle exhaust gases, non-food grade liquidCO

2, and decaying plant material. Ethylene is a

plant hormone and can be very damaging toplants, even at levels as low as 0.01 ppm. Con-centrations above 0.01 ppm in the greenhousemay cause accelerated ripening, reduced growth,internode shortening, leaf streaking, flowerdistortion and premature leaf and flower drop.

Ethylene measurement requires sophisticatedand expensive equipment such as portabledragger pumps. Some growers have successfullyused ethylene-sensitive plants like tomatoes todetect its presence.

Studies have shown that at high CO2 levels

there is a positive linear relationship betweenconcentration of carbon monoxide and ethyl-ene. The relationship assumes that undilutedflue gases with less than 5 ppm CO have lowerthan 0.01 ppm concentration of C

2H4. Most

commercial greenhouses use CO meters andother inexpensive CO devices to monitorindirectly the presence of ethylene.


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Oxides of nitrogen (NOx)

Very low levels of nitrogen oxides (NOx) are

always produced in the combustion process.Plants display visible leaf and head damagewhen exposed to concentrations higher than 0.5ppm for one to two days, particularly under lowlight intensity. Lower concentrations of NO

x or

a shorter exposure period can reduce growthspeed and yield.

Carbon monoxide (CO)

Carbon monoxide is an indicator of incompletenatural gas combustion. Although harmless toplants, concentrations above 50 ppm are harm-ful to humans. This gas is considered an “indica-tor pollutant” as its concentration increases withthe decline in combustion efficiency. This gas ismonitored accurately and CO

2 dosing is shut off

when CO concentration exceeds 2 ppm. Cali-brate and verify CO sensors at least annually tomaintain a safe working environment and toprevent crop losses (see Table 3-12).

Symptoms of Tissue Damage

Symptoms of tissue damage caused by indi-vidual pollutants have been well documented.Under greenhouse conditions, however, injuriesare usually caused by a combination of airpollutants. Symptoms include: abrasions, bub-bling, mottling, cupping and streaking ofleaves, abnormal flower development or drop,

multiple stem growth in the growing points(witches’ broom) and complete termination ofthe growing point. See colour photos 1, 2 and 3.

The plant’s sensitivity to air pollutants dependson the cultivar, stage of growth, plant balance,vigour, and climatic conditions. Plants grownunder low winter radiation without ventilationtend to be more sensitive to harmful concentra-tions of air pollutants than plants grown duringspring or summer light conditions when there ismore ventilation.

Measurement and Detection ofAir Pollutants

Concentration of selected pollutants can bemeasured with a dragger tube. This deviceutilizes a hand-held air pump that samples a setvolume of air over a calibrated tube (0.1ppm).The presence of a pollutant is indicated by acolor change in proportion to the detectedlevel. These devices are effective in detectingrelatively high concentrations of pollutants.Detection of low concentration of pollutantsrequires more complex analytical lab tests.Indicator plants are an effective and inexpen-sive alternative. For example, tomato flowersabscise even at very low ethylene concentra-tions (0.05 ppm).

Table 3-12. Maximum acceptable concentrations of some noxious gases for humans and plants (ppm).

Gas

Humans Short-term Exposure

Humans 8-Hour Limit

Plants Short-term Exposure

Plants Long-term Exposure

Carbon dioxide (CO2) 15,000 5,000 4500† 1600*

Carbon monoxide (CO) 100 25 100† N/A

Sulphur dioxide (SO2) 5 2 0.1† 0.015*

Hydrogen sulphide (H2S) 10 - 0.01† N/A

Ethylene (C2H4) a a 0.01† 0.02*

Nitrous oxide (N2O) - 25 0.5† / 0.01 to 0.1‡ 0.25*

Nitrogen dioxide (NO2) 1 - 0.2 to 2.0‡ 0.1*

Sources: *- Rijsdijk (1989); ** Workers’ Compensation Board of B.C. (2003); †- Langer et al. (1990); ‡ - Doring et al. (1990); a - ethylene acts as a simple asphyxiant through the displacement of oxygen.


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Strategies for Preventing AirPollutant Damage

• Verify CO alarm sensor every six months andensure boilers are calibrated at least once ayear.

• CO levels greater than 2 ppm in the flue gasare indicators of incomplete combustion andthe possibility of air pollutants in the green-house air. Flue gases containing this level ofCO should not be used for CO

2 enrichment

until the boiler flame has been adjusted.

• When using both natural gas and alternatefuels such as oil or diesel, recalibrate theburner each time the fuel is switched. Allowthe recommended time to elapse afterswitching back to natural gas, even as long asseveral weeks, until flue gases are free ofhydrocarbon residues.

• Ensure CO2 fans are turned off during

alternate fuel use to prevent air pollutantsfrom the boiler room being drawn into theCO

2 distribution system.

• Supply 10 m3 of air to boiler for each 1 m3 ofnatural gas burned to ensure efficient com-bustion. Provide outside air intake openingsof 6.25 cm2 per 2500 BTU furnace rating.

• Use liquid CO2 if feasible at start of the

crop. When there is limited ventilation avoiddosing flue gases at CO

2 concentrations

higher than 900 ppm.

• If pollutants are suspected, turn off the CO2

dosing and set a minimum vent if outsidetemperatures permit. Monitor crop changesin the growing point. Tag a number of plantsand mark the most recent leaf developmentrecording any changes over the period of aweek.

Irrigation and Nutrition

Volume and Frequency ofIrrigation Cycles

Water uptake is determined largely by transpira-tion rate. Almost all water taken up by theplant is lost through transpiration and only aminor proportion is used for growth. Lightintensities and related VPD’s drive transpira-tion rates; therefore, optimal volume andfrequency of irrigation cycles will vary withlight intensity. The growth stage of the plantand the volume and physical property of thegrowing medium will also influence irrigationrequirements.

Total IrrigationIrrigation volume changes seasonally from lessthan 1.0 L/m2/day in the winter and earlyspring, up to 5.0 L/m2/day in the spring and toover 5.0 L/m2/day during the summer. Volumein L/m2/day during winter, early spring and fallcan be calculated by multiplying accumulatedlight in joules/cm2/day X 3. From April toSeptember, volume can exceed this formula. Bycontinuously monitoring the percentage over-drain, the grower can assess and control theaccuracy of the irrigation volume.

The growth stage of the crop, its vigour, fruitload and other factors can affect the relation-ship between light and water uptake. A tall,rapidly growing crop with a large canopy willrequire more irrigation than a slow growing ornewly established crop. A high fruit load cansubstantially increase plant demand for water.

Frequency and Volume of IndividualIrrigation CyclesSimilar to total irrigation volume, the frequencyand volume of individual irrigation cycleschanges with different light intensities. Duringwinter and fall, relatively few irrigation cyclesare applied and the volume of individual cyclesvaries from 120 to 150 ml. Bright, sunnyweather promotes transpiration and increasesdemand for more frequent irrigations withreduced volume of individual cycles (up to 80


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ml). During mid-day, when light intensities arehighest, the time period between irrigations andthe volume of each cycle must be reduced evenfurther (see Table 3-13). By monitoring over-drain distribution throughout the day, thegrower can assess the accuracy of the irrigationfrequencies and volume of the cycles.

When growing in sawdust, water retention bythe sawdust is an important factor in determin-ing the frequency and duration of irrigation.Finer sawdust will retain more moisture thancoarser and therefore will require less frequentirrigation.

The time between irrigation cycles must be longenough to allow complete drainage but avoidwater deficit. Increasing the number of irriga-tion cycles ensures adequate supply of water,prevents excessively high concentrations of thenutrient solution in the drain, and replenishesthe void spaces on the sawdust with water.

The frequency with which irrigation is appliedand drained affects the aeration of the rootsystem. As roots respire, the content of carbondioxide increases in the void spaces of sawdust.The flow of irrigation solution will fill somevoids temporarily displacing the carbon dioxidewith a new supply of air.

Control of Irrigation

The most common methods of irrigation con-trol in commercial greenhouses are based ontime and light levels. Alternative methodsinclude monitoring changes in the plant weightor moisture content of the medium.

Control Based on TimeIn this system, the volume and frequency ofirrigation cycles are set manually. This is oftenused during establishment of the crop in thewinter season. It is also used to apply nightirrigation throughout the season.

Table 3-13. Summary of seasonal and daily control strategies for irrigation timing, volume and frequency; including the amounts of accumulated light required to initiate subsequent watering cycles.

Seasonal and 24-hr Control Strategies for Irrigation

SUNRISE MID-DAY LATE AFTERNOON SUNSET NIGHT

Production periods and range of light intensity for each period (joules/cm2/day)

Volume of total (L/m2/day) and individual (mL) irrigation cycle

accumulated light (joules) that triggers next

watering

Start time (hr) after sunrise % daily feed % daily OD

Time (hr) % daily feed % daily OD

Time (hr) % daily feed % daily OD

Stop time (hr) before sunset % daily feed % daily OD

Night watering*

% daily feed % daily OD

winter (Dec-Jan) to week 4 200-300

<1.0 L 100-120 ml

350-400

2-3 hr 20% 5%

11:00 -14:00

70% 10%

15:00-16:00

0% 0%

3 hr 0% 0%

10% 0%

spring (Feb-April) weeks 5 - 18 540-1800

< 5.0 L

120-150 ml 100-120

2-2.5 hr 15% 10%

10:00 - 15:00

70% 20%

16:00-17:30

15% 5%

2 hr 0% 0%

0% 0%

summer (May-Aug) weeks 19 - 35 1100-2700

>5.0 L

80-100 ml 70-120

2-2.5 hr 20% 15%

9:00-16:30

65% 25%

17:30-19:00

15% 10%

1.5 hr 0% 0%

0% 0%

fall (Sept-Nov) weeks 36-46 380-1400

< 5.0 L/

120-150 ml 100-150

2-2.5 hr 15% 10%

10:00-15:00

75% 20%

16:00-17:00

10% 5%

2.5 hr 0% 0%

0% 0%

Note: This table illustrates general principles of irrigation control as opposed to specific recommendations. See Pepper Production; Winter to Fall for more detailed information. * Night watering is typically applied only when pipe temperature is high and screens are not used.


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Control Based on Light LevelsAccumulated light is used to determinethe total irrigation volume and to initi-ate the next irrigation cycle. A new cycleis typically initiated after each 65 to 120accumulated joules/cm2 of light. Forthis system to be effective, the lightsensors need to be cleaned at least everythree months.

Irrigation control based on both accu-mulated light and time settings is themost commonly adopted practice incommercial operations. This controlstrategy provides flexible frequency ofirrigation cycles that follow closely theradiation curve.

Control Based on Monitoring the Per-centage and Distribution of Over-drain

How to set and measure the over-drain (OD)

Set up a minimum 4 to a maximum 15 over-drain stations/ha and average the collecteddata. This ensures that adjustments in theirrigation schedule or volume are based onresults obtained from a representative samplesize. Locate the stations in the middle of rowsand ensure the drainage station platform islevel, as platform tilt can negatively influencedrainage figures.

Figure 3-5. Overdrain monitoring station

Design a recording sheet that tracks both totalfeed and drain and the hourly over-drain per-centage. Mark both feed and drain containerswith 100 mL increments for quick and simplemonitoring of feed and drain volume (seeFigure 3-5).

Total over-drain

This system measures the amount of irrigationapplied and drained from the media and calcu-lates the total percentage of over-drain and thepercentage distribution of over-drain through-out the day.

Much like accumulated light, the total percent-age of over-drain will vary both seasonally anddaily. During winter, total over-drain volume is15 to 25% of the supplied feed volume;whereas during summer, it is 35 to 50% of thefeed volume (see Table 3-14).

Within each season, the total percentage of over-drain can be significantly affected by the dailychanges in accumulated light. During a brightsunny day, the total over-drain can range from 30to 50% of the feed; whereas during a dark day, itwill be reduced to 10 to 20% of the feed.

The total percentage of over-drain can also beadjusted based on the EC targets in the over-drain.

Table 3-14. Distribution of the percentage over-drain during a sunny spring day.

Time

OD (%)*

07:00 0% 08:00 1% 09:00 3% 10:00 6% 11:00 12% 12:00 30% 13:00 25% 14:00 22% 15:00 25% 16:00 15% 17:00 10%

*The percentage value for each time period may vary daily and seasonally; the distribution pattern should stay the same.


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Daily distribution of over-drain

To ensure optimal moisture supply throughoutthe day, the pattern of over-drain distributionshould follow closely the pattern of the lightcurve: i.e. increase until mid-day and declinethereafter. Monitoring the distribution of over-drain volume throughout the day is therefore ascritical as monitoring its total volume.

In the morning, moisture content in the growingmedia should be low and the first over-drain (1to 2%) should occur only after the third irriga-tion. Higher moisture content at this time ofthe day can cause excessive root pressure,which can reduce fruit quality and increase theincidence of pathogen infection.

Most of the over-drain should occur between12:00 to 16:00 hours. In the winter, expect 50to 65% over-drain during mid-day. In the springand summer, under high radiation and maxi-mum fruit loads, mid-day over-drain will rangefrom 30 to 50%. In the fall, the percentageover-drain will decrease in response to declin-ing radiation and plant vigour and deterioratingphysical properties of the growing media. Fullyor partially composted sawdust will hold morewater than the fresh sawdust.

Timing of the last two irrigations of the daydepends on available radiation. Apply the lasttwo irrigations approximately two hours aftersunset on a sunny day and two hours beforesunset on a dark day.

Effects of Excessive Frequencyand Inadequate Volume ofIrrigations

Too much moisture can lead to a lack of oxygenin the rooting media. Roots need oxygen forbreaking down assimilates and generating theenergy required for uptake of water and nutri-ents, nitrogen assimilation, growth and otherenergy-requiring processes. Root growth andfunction can be restricted as a result of over-watering. Low oxygen level in the rooting mediacan cause root rot and breakdown of the media.

Optimize oxygen supply by:

• Maintaining a careful balance between thesupply and demand for water. Ensure ampleoxygen supply during night and avoid over-watering during periods of high transpiration.

• The temperature of the irrigation solution isan important factor in determining theamount of oxygen available to roots. Thehigher the temperature of irrigation solution,the lower the oxygen content. Aerate andcontrol the temperature and proportion ofre-circulated solution used for irrigation.

Water deficit causes stomatal closure. Thisaffects assimilate production and the resultinguptake and distribution of water and nutrientsto the rest of the plant.

Irrigation Design and

LayoutThe irrigation system should be designed tomeet the needs of the plant at high fruit loadsand transpiration rates. Assuming one dripperper plant, the capacity of a single drippershould be at least 1.5 L/m2/hr, with a mini-mum of 5 - 6 and maximum 10 - 12 irrigationcycles /hr.

Each greenhouse should be equipped with twoirrigation pumps. These are used in rotation andprovide a backup system in the event that onefails. All components of the irrigation systemincluding pumps, filters, main and lateral linesshould be built with high quality and easily-maintained components. The main irrigationlines (7.5 – 20 cm PVC) that are buried shouldbe strong enough to withstand ground andwater hammer pressure. Row header lines (7.5cm) and row lines (1.9 cm) should be madefrom durable black polyethylene (see Figure3-6). White PVC is not suitable for exposedlines because it fosters algae growth under highlight intensity.

The irrigation solution is distributed to theplants through various sizes of drip tubes. A


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small diameter drip tube (0.1 cm) can be usedwhere the water source is clean. A larger tubediameter (0.15 cm) is preferred as it reduces therisk of plugging. Trickle or pressure emitters areattached to the drip tubes.

For trickle irrigation, a grooved plastic stake,provides accurate placement of the irrigationstream on the block and simultaneously aeratesthe water. It is a simple and reliable system, butthe output in ml/hr can be variable. Outputvariability in a new trickle system can reach10%; increasing to 25% in 2-year or older

Figure 3-6. Layout of a greenhouse irrigation system

Irrigation Dripper

Irrigation Pipe

Rockwool Block

on Sawdust

Heating Pipe

White PolyfilmFloor Covering

Drainage

Gully

Transversal slopefor slab drainage 0 to 3%

Figure 3-7. Growing slab/drainage collection layout

systems. Replace asystem thatreaches 25% orhigher variabilityin emitter output.Yield losses anddecrease in fruitquality outweighthe cost of re-placement.

Pressure-compen-sating emitters areactivated onlyafter water pres-sure at the emitterreaches 4 to 7 psi.This ensures a

consistent output. The effectiveness of thissystem depends on removing leaking emittersand keeping lines charged with solution at alltimes.

Proper profiling of the ground and drainage chan-nels are important components of an efficientirrigation system The rows should not be slopedmore then 0.5%. Cover drainage channels withplastic that is white on the top and black under-neath. A slight slope of 0.1 to 0.2% is all that isrequired to provide adequate drainage from bagsand nutrient leachate recovery. If the slope is toogreat, it can have a negative effect on water distri-bution between and within slabs (see Figure 3-7).


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Nutrition

Tanks and Fertilizer Mixing

Day storage tankDay storage tanks are usually large poly-linedsteel containers. A storage tank should have thecapacity to store two days’ water supply requiredfor peak conditions, i.e.10 – 12 L/m2/day. In-ground metal tanks and metal tanks located inthe header house must be protected from con-densation and exposure to corrosive fertilizersand acids used for making up feed solutions.

Tanks should be equipped with a circulationpump raised approximately 20 cm off thebottom and a drain to remove organic matterand other suspended materials from the bot-tom. To ensure aeration, allow returned waterto drop 2 to 3 ft into the tank. A provision forwarming or cooling the nutrient solution willprovide better control of the root environment.

Stock Solution TanksA typical large greenhouse has two solutiontanks “A” & “B”, each with 1000 to 4000Lcapacity, and a smaller “C” pH concentratetank of 100-400L plus an injector system. Onetank is sufficient for small greenhouses whenthe concentration of the fertilizer solution doesnot exceed the feed solution by more than X15.

The stock solutions in tanks A and B are con-centrated up to X100. In these tanks, fertilizerscontaining calcium (e. g. calcium nitrate) can-not be mixed with fertilizers containing phos-phates (monopotassium phosphate) or sul-phates as they will form insoluble precipitatesof calcium phosphates and calcium sulphates.These precipitates can plug the drip tubes andlead to nutrition deficiency. Other methods toprevent formation of precipitates include:adding small amounts of nitric acid to A & Btank, dissolving fertilizers individually in hotwater before adding to tanks and filling tankswith water before adding dissolved fertilizersand agitating while mixing.

Feeding FormulasThree feeding formulas are used to fertilizepeppers (see Table 3-15):

• “Start feed” is used to establish the plantuntil the beginning of harvest;

• “Picking formula” is used until the irrigationvolume increases to 5 L/m2/day;

• “High daily volume formula” is used in earlysummer when the daily feed volume exceeds5 L/m2/day for an extended period of time.

Supplemental Nutritional Notes• Peppers are sensitive to high sodium (Na)

concentrations. Do not exceed 5 mmol of Naper liter.

• Manganese (Mn) is available to plants fromthe feed and sawdust media. Plants absorbMn more readily at low pH (<5) than at highpH (>7). Prolonged periods of low pH (5and lower) in the root zone can lead tomanganese toxicity. Manganese toxicityappears as burn spots on the leaves near thetop of the plant. Warm areas of the green-house where there is a high transpiration ratetend to show the damage first.

• Boron (B) is absorbed only by the young roottips and poor root growth can lead to a Bdeficiency. B deficiency is expressed by ayellow discoloration of the growing tips 30cm below the head and by browned leafveins. The latter condition is highly visiblewhen the leaves are held to the light. Stimu-lating root pressure and reducing the pH willaid the boron uptake process.

• Low light levels and VPD less than 3 duringthe first set can negatively affect calcium(Ca) uptake, reducing thickness of cell walls.The resulting fruit has reduced shelf life dueto premature water loss and fruit shrinkage.Monitor the nutrient solution to ensure ionsthat can influence Ca uptake are in balance(NH

4, K, Na, Cl and Mg).


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Electrical Conductivity (EC)When dissolved in water, fertilizers (inorganicsalts) ionize forming charged particles calledions: cations have a positive charge, anions, anegative charge. Potassium nitrate dissolvesforming an ionized solution of K+ cations andNO

3

- anions. Ionized solutions can conductelectricity whereas distilled or de-ionizedsolutions cannot. The ionized solutions ofsome fertilizers conduct better then others andsome solutions, e.g. urea, do not conductelectricity at all.

Both the total concentration and compositionof dissolved salts affect the electrical conduc-tivity (EC) of a solution. EC of a solutionincreases with an increase in the total concen-tration of the solutes but not all solutes areequal. For example, potassium ions stronglyinfluence electrical conductivity, whereas

nitrate ions do not. The EC of a solutionreflects the aggregate conductivity of all thesolutes present and does not differentiatebetween them.

The EC is expressed most frequently inmilliSiemens per cm of solution (mS/cm).

A typical EC feed for peppers ranges from 2.4to 3.5 mS. Osmotic pressure created in thisrange of nutrient concentration optimizesabsorption of the nutrients by the roots.

Measurement andInterpretation of EC Value

EC is affected by temperature of the solutionand mineral composition of the water. ECvalue increases by 2% in response to a tempera-ture increase of 1oC. Modern EC meters havea built-in feature that adjusts the EC valueaccording to the solution temperature. Older

Table 3-15. A general guideline for stock solutions of feeding formulas for peppers

grown in sawdust and rockwool. Each tank holds 1000 L of concentrate which is diluted X 100 to make up feeding solution. Final volume of feed solution is 100,000 L @ EC 3.0.

Start Feed Formula

Picking Formula

High Daily Volume Formula 5 L/m2

Tank A calcium nitrate potassium nitrate iron 6% ammonium nitrate*

125 kg 25 kg 2 kg 4 kg

100 kg 25 kg 1.5 kg

0 to 2 kg

100 to 120 kg

25 kg 1.5 kg

0 to 4 kg

Tank B potassium nitrate monopotassium phosphate potassium sulphate magnesium sulphate manganese sulphate zinc sulphate boron copper sulphate sodium molybdate

35 kg 25 kg

-- 37 kg

170 grams 150 grams 350 grams 19 grams 12 grams

50 kg 20 kg 10 kg 25 kg

170 grams 150 grams 350 grams 14 grams 12 grams

25 to 50 kg 15 to 20 kg 0 to 10 kg

25 to 30 kg 100 to 200 grams 100 to 150 grams 300 to 350 grams

10 to 20 grams 5 to 12 grams

Note: Modifications to each formula should be based on results of weekly or bi-weekly analyses of over-drain and/or feed. * Use ammonium nitrate addition if pH in the slab needs to be lowered and when the feed water is buffered with bicarbonates. Adapted from: Diagnosis of Mineral Disorders in Plant Volume 3 -- Glasshouse Crops. By G. Winsor and Peter Adams.


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models rely on standard reading taken typicallyat 25oC and may require correcting. The watersource has its own EC value. Depending on theamount of naturally dissolved ions in the water,the EC can range from 0.1 to 1.0 mS/cm. TheEC value of the water should be subtractedfrom the EC value of the feed and drain.

Seasonal and Daily Trends in EC

Feed EC is usually high (3.0) during low lightintensity in winter, spring and fall and is reducedto about 2.5 during high light intensity in late falland summer (see Table 3-16). Feed EC can fallto 2.5 during sunny/cloudy weather when fruitloads are high, drain EC is lower than 4.5, andfeed volume is >5 L/m2/day (see Table 3-17).Weekly nutrient analysis of the drain solution(OD) is recommended, especially during earlyestablishment, in late fall and when using a re-circulation system. When feed EC falls from 3.0to 2.5, the concentration of micronutrients isreduced. Increase concentrations of

micronutrients by 25% to maintain their targetlevels. All changes to EC’s should be doneincrementally over the course of a week.

Effect of EC on Growth Balance

The strength and composition of the feedexpressed as EC, in conjunction with lightlevels, can be an effective management tool forsteering the plant into vegetative or generativebalance:

• low EC (<2.8) promotes vegetative growth;

• high EC (>3.0) promotes generative growth,specifically initiation of flowers.

Effect of EC on Taste andShelf Life

EC has a direct influence on the taste, shelf lifeand size of fruit:

• low EC (<2.5) is associated with cuticlecracking and reduced shelf life;

• high EC (>3) produces fruit with a highconcentration of sugars and other tastedetermining solutes;

• higher EC (>5) can reduce fruit size andincrease incidence of BER.

Monitoring Crop Nutrition

Monitor EC of the feed and drain daily. Thefrequency of nutrient analysis depends onmanagement of the drain; i.e. waste or re-circulation. When draining to waste, analyzethe leachates weekly for lower than 5L/m2/dayfeed volume, and reduce to a minimum bi-weekly for higher than 5L/m2/day feed vol-ume. When re-circulating, analyze the over-drain solutions weekly to prevent potential ionimbalances (see Table 3-18). Analysis of thedrain is the basis for determining the nutritionalrequirements of the crop. Feed and tissueanalyses are done occasionally, and providevaluable information on possible macro- ormicro-elements deficiencies or excesses (seeTable 3-19).

Table 3-16. Seasonal range of EC targets for

feed and drain.

Feed Drain Volume

Winter 3.0 – 3.5 3.0 - 4.5 <5L/m2

Spring 2.8 – 3.0 3.2 - 3.5 >5L/m2

Summer 2.5 – 3.0 3.0 - 3.5 >5L/m2

Fall 2.8 – 3.0 3.2 - 3.5 <5L/m2

Table 3-17. Daily range in feed EC for bright

and dull days.

Feed volume <5L/m2

Dull Day *

Feed volume >5L/m2

Bright Day** Dawn 2.5 – 3.0 2.5 – 3.0

Mid-day 2.5 – 3.0 2.5 – 2.8

Afternoon 2.5 – 3.0 2.5 – 2.8

Night 2.8 - 3.0 3.0 – 3.5

* Dull Day; radiation level at 400 watts, daily cumulative light ~1000 joules ** Bright Day; radiation level at 800 watts, daily cumulative light ~ 2000 joules


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The feed composition needs adjustment whenthe content of a specific ion in a drain changes10 to 25%. Plotting the distribution of indi-vidual ions over time helps identify nutritionaltrends and provides long-term information formaking irrigation management decisions. The

growth stages of the crop, climate control setpoints and disease or pest control practicesneed to be considered prior to implementingany changes.

The pH

The pH value is a measure of acidity or alkalin-ity of the solution. The solution is acidic if thepH is less than 7, neutral if equal to 7, andalkaline if greater than 7. The pH value deter-mines, among other things, the solubility ofvarious nutrients in the solution and theiravailability for root uptake. At optimal feed pH(5.8 to 6.2), most of nutrients are readilyavailable to the plant (see Figure 3-8). Opti-mum drain pH ranges from 6.2 to 6.8.

Nitrogen source (NH4 or NO

3), can influence

the pH of the root zone and drain. Varyingproportions of ammonium in the feed canchange the pH in the drain (see Table 3-20).

Measuring and Buffering theFeed Solution

Collection of feed and drain samples is de-scribed on page 36. Daily monitoring of ECand pH of both feed and drain is recom-mended.

There are a number of buffers that can be usedto maintain the feed solution within the opti-mum pH range of 5.8 to 6.2. The direction ofpH change is determined by the concentrationof bicarbonates and carbonates in the water.Concentrations below 50 mg/L can cause pHfluctuation in the drain and bicarbonates orcarbonates may need to be added to stabilizethe feed formulation. Acidification is usuallyrequired to correct pH if the bicarbonateconcentration is above 100 mg/L.

Buffering the day storage tank with 2.5 – 5 kgof potassium bicarbonate per 100,000L of feedsolution can stabilize the pH in the root zoneand in the drain. Sodium bicarbonate can alsobe used providing the sodium concentrationremains within the optimum drain targets.Carbonates should be introduced in the day

Table 3-18. Target over-drain levels in drain to waste and re-circulation system.

EC, pH and Nutrient Ions

Drain To Waste and Re-circulation Targets

EC mS/cm PH NH4

+ mmol/L K+ mmol/L K/Ca ratio Ca++ mmol/L Na+ mmol/L Mg++ mmol/L NO3

- mmol/L Cl- mmol/L SO2

= mmol/L HCO3

- mmol/L P mmol/L Fe µmol/L Mn µmol/L Zn µmol/L B µmol/L Cu µmol/L Mo µmol/L

2.5 to 3.5 5.5 to 6.0 0.1 to 0.5 6.0 to 9.0

>1.5 5.5 to 8.5 1.0 to 5.0

2.25 to 4.25 15 to 25 1.0 to 5.0 2.5 to 5.0 0.1 to 1.0 0.6 to 1.2 15 to 30 5 to 10 5 to 10

45 to 75 0.5 to 1.5

0.5

Table 3-19. Target levels for tissue analysis of sweet peppers.

Element

Normal Range

Deficiency

Nitrogen % Phosphorus % Potassium % Calcium % Magnesium % Sulphur % Boron ppm Iron ppm Manganese ppm Zinc ppm Copper ppm Molybdenum*

3.5 to 5.5 0.35 to 0.8

3 to 6 1.5 to 3.5 0.35 to 0.8 0.3 to 0.6 30 to 90 80 to 200

100 to 300 40 to 100

6 to 20

2 0.2 2.0 1.0 0.3 0.2 20 60 20 25 4

*Limited information on molybdenum. Younger leaves become yellow green associated with pH<5.


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storage tank at least 12 hours before mixing thefeed. Dosing bicarbonates in the feed tanks isnot recommended as precipitates can form andplug the dripper emitters.

Phosphoric and nitric acid are the most fre-quently used buffers when the feed solution istoo alkaline. They provide nutrients as well aslowering the pH. Sulphuric acid and hydro-chloric acid can also be used providing they arehorticultural grade and free of contaminants.Sulphuric acid should not be used if the naturalwater source already contains sulphates inconcentrations higher than 100 mg/L (ppm).When re-circulating, monitor the chloride andsulphate ions to prevent their build up. Theamount of acid required to maintain pH of 5.8to 6.2 depends on the water quality and con-centration of the fertilizers. The “C” tank is

used to dose acids or basesand the solution is usuallydiluted 10 to 15 times byvolume.

Water QualityThe suitability of water forgreenhouse use is determinedby pH, EC and the presenceand concentration of selectedions, suspended solids, andmicro-organisms (see Table 3-21). Water quality failing theguidelines may not be suitablefor greenhouse use without

treatment or modification.

Key Unwanted Ions

Sodium and chloride are the two key unwantedions. At concentrations above acceptable thresh-olds, these ions can compete for uptake ofessential ions and restrict plant growth. Calcium(Ca), magnesium (Mg) and sulphate (SO

4) and

occasionally trace elements can also be found insignificant concentrations in water. Water sam-ples should be analyzed and the results factoredinto the composition of greenhouse feed.

Frequency of water analysis depends primarilyon the water source and past records. Forexample, water quality from sources affected byseasonal rainfall should be monitored fre-quently whereas municipal water need only be

monitored occasionally.

Water Sources

Water used for production ofgreenhouse vegetables mayoriginate from the followingsources: municipal drinkingwater, rain, wells, dugouts,streams, rivers, lakes, re-circulation water and a combi-nation of the above.

Municipal WaterAlthough often used in green-house production, municipal

Figure 3-8. How medium pH affects the availability of plant nutrients.

Table 3-20. Preferred nitrogen sources for pH control

Range of pH in OD

Nitrogen form and source

% NH4+ of total

nitrogen feed Irrigation volume

L/m2/day

>6.5 Calcium nitrate,*

ammonium nitrate or urea

8% <5

6.2 – 6.5

Calcium nitrate with 1.1% NH4

+ ; decrease ammonium nitrate or

urea

4%

>5

6.0 – 6.2

Reduce calcium nitrate with 1.1% NH4

+; remove all ammonium

nitrate or urea

4% >5

<6.0

Use only NH4+ free

calcium nitrate <4%

>5

* Regular grade calcium nitrate has 15.1% nitrogen (1.1% in the form of ammonium)


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drinking water can be expensive and its compo-sition can change depending on seasonal de-mands. This can affect the composition andbuffering requirements of the greenhouse feed.Most municipal water has low micro-organismlevels as a result of chlorination and filtration.High concentrations of chlorines can influencepH stability and directly affect root health.

RainwaterWater captured from the greenhouse roof cansupply a fraction of greenhouse water demand.The percentage of rainwater supply can becalculated based on an average rainfall formula:rainfall 1mm = 1 liter/m2 (for B.C.: 1000 mmrainfall/year=10,000 m3/ha).

Rainwater may contain soil particles that carrypathogens. It may also contain high levels ofZn originating from galvanized steel construc-tion. Zn concentrations higher than 2.0 mg/Lcan reduce yield significantly (up to 10%).Rainwater has a low buffering capacity.

Well WaterWell water can contain dis-solved methane in concentra-tions higher than 0.1 mg/L.The drippers can plug whenbacteria oxidize the methane.

A similar problem may occurin the presence of iron (Fe>0.1mg/L). This can besolved by water aeration orchemical pre-treatment.High silicon (Si) levels inwell water can foster algaegrowth, especially whenstored in an uncovered tank,resulting in plugged irriga-tion lines.

The quality of ground waterfrom shallow wells canchange throughout the

season in response to rainfall cycles. Concentra-tions of calcium (Ca), magnesium (Mg), andsulphate (SO

4) can rise to the point where the

feed formula may require adjustment. Elevatedconcentration of these ions can also increase thepossibility of precipitates’ forming and pluggingthe dripper lines. High concentrations of sodium(Na) and chloride (Cl) are found occasionally inwell water and can negatively affect irrigationsuitability.

Dugouts, Streams, Rivers, and LakesWater collected from a variety of surfacesources can also be used for irrigation. Organicsuspensions in these water sources are oftenhigh and may include root disease organismssuch as Pythium spp. Surface water runoff inagricultural areas also has the potential forfertilizer and herbicide contamination. Wateroriginating from these sources requires sandfiltration and purification to prevent algalblooms and waterborne pathogens.

Table 3-21. BCMAFF* Greenhouse Irrigation Water Quality Guidelines

Parameter Upper Limit Optimum Range

pH EC SAR (sodium absorption ratio) Alkalinity Bicarbonate equivalent Calcium Magnesium Iron Manganese Boron Zinc Copper Molybdenum Sulfate Chloride*** Sodium

< 5.0 or > 10.0 1.0 mS/cm 4 mg/L** 200 mg/L 150 mg/L 120 mg/L 24 mg/L 5 mg/L

2.0 mg/L 0.8 mg/L 2.0 mg/L 0.2 mg/L

0.07 mg/L 240 mg/L 140 mg/L 50 mg/L

5 – 7 < 0.1 mS/cm 0 to 4 mg/L

0 to 100 mg/L 30 to 50 mg/L 40 to 120 mg/L

6 to 24 mg/L 1 to 2 mg/L

0.2 to 0.7 mg/L 0.2 to 0.5 mg/L 0.1 to 0.2 mg/L 0.8 to 0.15 mg/L

0.02 to 0.05 mg/L 24 to 240 mg/L

0 to 50 mg/L 0 to 30 mg/L

* B.C. Ministry of Agriculture, Food and Fisheries ** mg/L = ppm. *** Chlorine used for water purification is different from chloride ions. Water supplied for greenhouse use should contain less than 1 ppm of chlorine. Note: For more detailed information see the BC Trickle Irrigation Manual, 1999


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Growing Media

Media for Propagation

Rockwool “kiem plugs” (2x2x2.7 cm; 240 /tray) and propagation blocks (7.5x7.5x6.5 cm)are the standard seeding media for peppers.Peat blends can also be used in 10 cm diameterplastic pots. A good medium for seedlings oryoung plants must be uniform, well-drained,pathogen-free and have good moisture and airholding capacity.

Properties of a Good GrowingMedium

There are a number of excellent hydroponicmedia including: sawdust, rockwool, perlite,pumice, foam and coco-fibre. The key charac-teristics of a good medium include:

• large pores with 60 to 80% water holdingcapacity and 20 to 40% air capacity for freedrainage;

• respond well to temperature changes andremain chemically inert for good nutrient andpH control;

• consistent physical quality that can be sus-tained through the growing season;

• light-weight for ease of handling;

• pathogen-free;

• environmentally friendly for easy disposal; and

• inexpensive.

Each medium has pros & cons. When theirperformance is similar, cost becomes a keyconsideration.

Sawdust as a growing mediumSawdust is the main growing medium used in theB.C. greenhouse vegetable industry. Bags filledwith sawdust provide an anchor for the plant andan environment for root development.

Yellow cedar sawdust is the industry standardbecause it decomposes slowly providing a well-drained and aerated medium throughout thecropping cycle. Douglas fir, hemlock and pinesawdust break down faster. This may result in

poor media aeration and lead to root death.Sawdust from western red cedar is not recom-mended because of its relatively high level ofsecondary plant metabolites. Although yellowcedar sawdust meets most of the above criteria,it does have some disadvantages. For example,non-pathogenic fungi from fresh sawdust oftencolonize the surface of the rockwool block andform a water repellant coat that reduces theeffectiveness of irrigation.

Use only horticulture grade sawdust and checkit’s conductivity for the presence of ocean salt.Leaching the bags with fresh water beforeplanting can reduce salt concentration in thesawdust. Horticultural grade sawdust should befree of phytotoxic contaminants such as anti-sapstain fungicides and wood preservatives.

An analysis for manganese (Mn) is also recom-mended as this mineral can accumulate in thewood to levels that are toxic to plants. If high Mnin sawdust leads to plant tissue Mn levels above500 ppm in the youngest leaves, adjust the com-position of the irrigation feed accordingly.

Containers for SawdustWhite plastic “pillow” bags are available in vari-ous sizes. The sawdust volume of a bag can varyfrom 10 to 25 liters and hold 2 to 3 pepper plants.Smaller sawdust volumes allow greater flexibilityin controlling the daily EC and pH levels.

The depth of the sawdust is a critical factor forproper drainage and aeration. A target depth of12 cm allows for some settling and decomposi-tion as the season progresses. Sawdust bags thatare inadequately filled and aligned will be tooshallow (<10cm) and drain poorly.

Ensure good in-ground drainage and maintain aproper slope for surface drainage of nutrients tore-circulating catch basins. To maintain a uni-form nutrient distribution in the sawdust bag,ensure there is a transverse slope not greaterthan 1%. The ground should be laser-profiledand covered with white floor plastic to allow ashallow trench (8-18 cm) between the doublerow of plants. Thin (1cm) styrofoam can be usedto ensure a flat insulated profile for the slab.


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In order to ensure proper rooting conditions,the media should be ‘charged’ with a nutrientsolution prior to planting out. This initial wettingactivates bacteria that release CO

2, reducing the

conductivity of the drain solution by 0.5 to 1.0EC. The effect of the microflora on the EC levelwill only last for several weeks and can becompensated by adjusting the feed solution.When the sawdust is uniformly wet, cut drainageholes between the drippers at the bottom of thebag facing the drainage trench. The holes shouldextend to the bottom of the bag.

Rockwool as a Growing MediumRockwool is manufactured by heating rocks toa high temperature and spinning them intofibres of different densities and vertical orhorizontal alignment. Rockwool meets most ofthe key criteria for a good growing medium. Ithas high air-holding capacity when saturatedwith nutrient solution (65% water:35% air -80% water:20% air) and is used worldwide inhydroponic systems. It is more expensive thanyellow cedar sawdust. It also tends to becomesaturated more easily in changing weather

conditions, leading to increased root pressure,decreased fruit quality and increased incidenceof root pathogen infections.

A new rockwool product now available is acombination of horizontal fibre alignment on thetop and vertical alignment on the bottom of theslab. The new product can maintain 80% watercontent and provide more uniform drainage.

Greenhouse pepper production requires 14 to16L of rockwool/m2. Average growth and yieldcan be obtained, however, with as little as 5L/m2. Such a small volume leaves little room forerrors in irrigation scheduling. The size ofstandard ‘slabs’ ranges from 15 - 45 cm wide,7.5 -10 cm high and 90 - 100 cm long. Thereare several densities that permit extended useof this medium. Low-density slabs are used forone year and discarded; higher density slabsmay be pasteurized and re-used for severalyears. The option exists to re-use them withoutsterilization if the previous crop was free ofproblems. Slabs that have lost their depth fromhandling can be double stacked to create anadequate 7cm depth.


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CultivarsAll sweet bell pepper cultivars produce greenfruit that matures to red, yellow, or orange. Allcultivars have specific climate requirements,therefore, mixing cultivars in the same green-house is not recommended. Development ofnew greenhouse pepper cultivars is a highlycompetitive business between a relatively smallnumber of seed companies. As a result,cultivars tend to change every few years. Grow-ers must keep in touch with latest develop-ments through contact with their seed suppliers.The main seed suppliers are listed in Table 4-1.

Cultivar characteristics include: tolerance tostrains of pepper mild mottle virus (PMMV-strains TM0, TM1, TM2, TM3), yield, fruitcharacters, fruit set requirements and labourrequirements.

Propagation

Virus Susceptibility

Pepper seedlings are susceptible to viruses.They can be transmitted on: seed, propagationequipment, workers’ hands and pruning equip-ment. Control measures include:

SeedUse heat-treated seed or soak untreated seed in a10% solution of trisodium phosphate (TSP ; seepage 124). TSP considerably reduces seedgermination. Over-seed to compensate forreduced germination and to ensure enoughplants.

Propagation equipmentEnsure the propagation area and all equipment,including packing cases, trailers, etc. arecleaned with Virkon® or another proven prod-uct that will kill viruses.

Hands and pruning equipmentDip hands and pruning equipment in 10%solution of skim milk powder (100 g/L) before

Seed Supplier Phone # Fax # Website

De Ruiter 614-459-1498 614-442-1716 www.deruiterseeds.com

Enza Zaden c/o Westgro c/o Westgro www.enzazaden.nl

Growers’ Consulting 519-326-6654 519-326-2480 Rijk Zwaan c/o Terralink c/o Terralink www.rijkzwaan.com

Syngenta 208-327-7239 208-378-6625 www.rogersadvantage.com

Terralink 604-864-9044 604-864-8418 www.terralink-horticulture.com

Western Seed Americas

203-226-3050 540-775-0435

203-454-3317 540-775-0439

www.westernseedamericas.com

Westgro 604-940-0290 604-940-0258 www.growercentral.com

Table 4-1. Seed sources for greenhouse pepper cultivars.


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handling seedlings. The 35% or greater proteinfound in skim milk coats the virus and rendersit non-infectious (see page 124).

Time of Seeding

Mid-October to early November are the stand-ard seeding dates for peppers propagated undersupplemental light. This allows time to producea large enough seedling (7.5 weeks) for plantingout by mid-December. However, for newgreenhouses with good winter light, seedingbetween October 5 and 10 may enable fruit setby the first week of January.

Seed Germination

Germinate the seeds in 25 mm x 30 mmrockwool plugs. Wet the plugs with an EC of 2.0to 2.2 mS/cm and a pH of 6 to 7. Maintain themedia temperature at 26oC and fertilizer solutionat 25oC until the plants emerge, then reducemedia temperature to 24oC night, 25oC day.Keep RH at 60 to 80%. Ensure the plugs remainmoistened to at least 70% of their saturatedweight during the germination process. Avoidputting the trays on the floor as doing so reducesdrainage and oxygen levels in the plug.

Stop watering at least one day before plantingthe plugs in blocks to avoid stem cracking.Stem cracks increase a chance of Fusarium

infection. Consider using Mycostop (KemiraAgro Oy) as a biological aid for preventingFusarium infection.

Provide supplemental light 15 w/m2 PAR(measured at seedling level) for 16 hours/dayto promote vegetative growth. Avoid over-crowding which could cause seedlings tostretch. End the lighting cycle with naturalsunset. Reduce lighting to 4 hours/day afterseedlings are spaced out, and only use addi-tional lighting during the day under poor naturallight conditions (<150 joules/cm2/day). Seecolour photo 4.

Planting Into Block

The seedling plugs are ready for transfer intorockwool blocks (75 to100 mm) once the firsttrue leaves appear. Wash/flush the blocks withover-head water two days before planting toremove possible toxic by-products from themanufacturing process. Next, thoroughly wetthe blocks with 2.5 EC fertilizer solution priorto transplanting.

Inverting or “flipping” seedling plugs whentransplanting into rockwool blocks shortens thestem and provides extra rooting area along itThis may delay plants 3 to 4 days, but flippedseedlings are shorter and sturdier and less likelyto fall over when handled.

The floor of the greenhouse where the blocksare grown should be covered with white poly toensure a good reflective surface and to preventroot rot contamination. After planting inblocks, apply feed solution generously to ensuregood connection between plug and block. Feedtemperature should be 20oC.

Approximately one week before the plants aremoved from the propagation area to the green-house, supplemental lighting can be reduced toa natural light cycle or discontinued. This willresult in fewer problems in the rooting-in phase.Abrupt changes from an environment with lightsupplement to one without, causes a “lightshock” that is exhibited as yellowing of lowerleaves and premature leaf drop. Over-use ofsupplemental light in the rooting phase can alsocause faster plant development, some leafbubbling and more stretching .

A well-developed root system (see colour photo5) and large leaf area of the transplant is criti-cal to achieve optimum yield and fruit qualitythroughout the growing season. Overcrowdingcan decrease transplant quality and lead to theloss of lower leaves and stretching of plants.Leaf loss can also result from cool growingtemperatures.


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Transferring to Greenhouse

At 30 days after seeding, space plants to 20/m2

and target block temperature of 21 to 22 oC.After moving the plants from the propagationarea to the greenhouse, lower the air tempera-ture to 20 to 20.5 oC for several days to reducestress related to the change of RH regimes.Lowering the temperature helps to slow downthe transpiration rate. Once acclimatized, targetthe following temperatures and VPD (may varywith cultivar): root zone 21°C, day air 23 to26°C (boost at 11:00 to 14:00), night air 21°C,ADT 21 to 22°C and VPD 3 to 7g/m3.

A six-week-old plant, weighing 40 g, is theminimum requirement for transplant age.However, a 7- to 7.5-week-old plant will pro-vide a better generative start (see colour photo6). They have thicker leaves and more drymatter. Ideally, seedlings should be 25 to 30 cmtall and start branching at the 5th to 7th leafnode. Grade out stunted plants with any abnor-mal growth (potential virus). Small but healthyseedlings can be planted out on west or southwalls or warmer areas of the greenhouse wherethey can catch up.

Once rockwool blocks dry down to 70% of theirsaturated weight, water plants with a completenutrient solution. Feed from the top of the blockto aid in flushing salts and contaminants fromthe block. Over-head watering at this stage alsohelps to restore oxygen levels to the rockwoolblock and promote root growth. Don’t userecirculated solution at this stage because of therisk of introducing root pathogens.

Maintain CO2 levels at 400 to 500 ppm with

liquid CO2.

If the CO2 is supplied by a boiler,

avoid levels greater than 1000 ppm, especiallyin a new, tightly-sealed greenhouse. Seedlingsare very sensitive to combustion by-productgases like ethylene. Provide adequate boilerpurging time when switching from oil fuel tonatural gas to prevent unburned hydrocarbonsfrom causing pollution damage to the plants.

Fungus gnat larvae can tunnel into seedlingcrowns and cause considerable damage to

developing roots (see colour photo 7). Startcontrol of fungus gnats during propagation byusing yellow sticky traps, Hypoaspsis spp. andnematodes (see page 91).

Acclimatization in theProduction Greenhouse

Plants moved to the production greenhouse arespaced wider apart and must cope with signifi-cant changes in microclimate (temperature, RHand light levels). This can be very stressful tothe seedlings unless they are acclimatized totheir new environment over a period of severaldays. Start by lowering the temperature andminimum pipe to promote buildup of RH. Usea fixed or moveable screen to create a moremoderate climate. This will reduce transplantstress related to extreme climate conditions.

To ensure rapid rooting the rock wool blockneeds to be firmly positioned in the sawdust. Slitthe plastic bag and insert the rock wool block sothe plastic edges of the bag are holding the blocksecurely in place. This method of anchoring theblock in the sawdust bag is preferred to cutting ahole in the bag and setting the block on thesawdust. It creates a better microclimate forrooting and protects plants from falling overbefore they are firmly rooted.

Insert irrigation drippers vertically intorockwool block so that nutrient solution willflow into the block rather than drip onto thebag or ground plastic. Irrigate with long inter-vals between cycles to promote contact withthe sawdust slab and encourage root develop-ment but do not over-saturate the block. Thenumber of irrigation cycles will depend on pipetemperatures, and pre-charging of sawdust bagswith irrigation solution. Typically, 2 to 3irrigations over a 24-hr period are sufficient; therock wool block should not be allowed to dryout. As soon as the first roots appear, reducethe irrigation to encourage roots to search forwater, but be careful not to let the media dryout during this process. See colour photo 8.


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Crop Management

Planting Density

Plant peppers in 5 rows per 8 m bay. For cropsplanted out before May, maintain a density of3.3 to 3.5 plants/m2 (6.5 to 7.1 stems/m2) with38 to 39 cm between plants. For crops plantedafter May, a spacing of 2 plants/m2 and 4shoots per plant may be used. Plant density isbased on light availability (location or green-house design) e.g. density of red cultivars in anold greenhouse may be 6.0 stems/m2; in a newhouse it may be 6.4 stems/m2 or higher.

Stem Densities

The currently recommended plant density is 3.3to 3.5 plants/m2 using a system of two stems perplant. Past research demonstrated that the two-stem system was the most productive. The optionof using 3 or 4 stems per plant with a V- systemcan save on plant costs. See colour photo 9.Each of the systems has specific plant manage-ment requirements.

• In the 3 to 4-stem system; fruit set is delayedcompared to the two-stem system for thesame seeding dates. The plant needs to pro-duce extra shoots before it is allowed to setfruit. Saving on plants/m2 can be offset by adelayed first harvest and this delay should befactored into the net $/m2 for the crop.

• Plants are seeded earlier for the 4-stemsystem, as it requires more leaves than two-stem system before 1st fruit set.

• B.C.’s experience with 4-stem system sug-gests that total yield in kg/m2 and fruit sizeare similar to the two-stem system.

• Plant height tends to be shorter in the 3 and4-stem system and requires less maintenancethan the 2-stem system. Sunscald appearsless frequently in 3 and 4 stem systemsbecause the plants have more leaves toprovide shade.

• Uneven stems is an issue with the 4-stemsystem. Application of similar string tensionto the stems and tying the stems at the same

time can reduce height differences. Regulateindividual stem growth by thinning fruit orflowers or by removing the growing point ofthe strongest stem.

• In the 4-stem system the loss of one plantcan create a large gap in the row.

• Several cultivars have been successfullygrown in the 4-stem system in South CoastalB.C.

In the 3 or 4 stem system, extra stems areremoved in late summer to compensate fordeclining light.

Training and Pruning in theTwo-stem System

The young transplants naturally branch into twoor occasionally, three shoots. This occurs be-tween the 5th & 8th leaf. Plants are initiallytrained to 2 or 3 stems each. At about 4 weeksafter planting out, select the two strongestshoots. Tie the stems to strings supported fromoverhead wires at 3.5 to 4.0 m. Clips should beavoided when initially tying the plant stem to thewire as they are prone to failure, resulting inplant slippage. A loose slipknot is recommendedto avoid the string cutting into the stem as itgrows. Open stem wound sites can be infectedwith Fusarium stem rot. If clips are used, alter-nate between twisting and clipping to provide asecure stem support. The stem will requiretwisting around the string every 10 to 14 days.

Prune side shoots that are 10 to 15 cm belowthe growing head. Pruning too close to the headis labour inefficient and can cause damage todeveloping flowers. Pruning slows down thetranspiration process, which in turn can nega-tively influence VPDs. In order to limit thisnegative effect, prune alternate rows on arotational basis. If a head is damaged throughthe course of cropping, a side shoot can betrained as the new head.

Remove side shoots allowing one leaf per shootfor better light penetration and larger flowerdevelopment. The option of leaving 2 to 3leaves per shoot should be considered starting


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in March. This provides a fuller canopy forbetter protection against sunscald. Start prun-ing to 2 or 3 leaves early enough to protect fruitin rows with edge exposure and for cultivarsthat do not produce a full leaf canopy. Removesecondary and tertiary axil flowers as they tendto produce lower quality fruit than the primaryflowers, reducing overall growth speed andplant balance.

Dip hands and pruning equipment in solutionof 10% skim milk powder (100 g/L) beforehandling plants to prevent virus spread. Milkshould be used at least until June, but if there isa previous history of virus or cultivar suscepti-bility, milk use should be continued through toSeptember.

A vigorous, 60 to 75-cm-tall plant with 4-5 leafaxils above the first fork is ready to set fruit.Ideally allow one fruit to set for every twoleaves. Maintenance of correct fruit load willprevent the pepper plant from producing extraside shoots and will optimize the use of labour.

Maintain fruit balance when removing anymisshapen fruit. Avoid too early removal of thefruit that will cause plant to set again; butprevent the unmarketable fruit reaching largerthan 4 cm diameter as that would be a waste oflimited assimilate reserves.

Management of Extra Stems inthe Two-stem System

The system involves adding extra shoots to theplant during the growing season, thereby in-creasing the plant head density per m2 as lightlevels increase.

• Start during re-growth period after the 1st or2nd set is established around week 8 to 9.Then add an extra stem to every 7th head inthe row.

• Remove tip (head) growth and allow sideshoots to grow.

• Select the best two heads.

• One of the new heads can grow on the oldstring; fasten a new string to the extra head.

• The picking pattern is very stable with thissystem

• Fruit size is not affected

• The 2nd set is delayed as a result of“deheading” the main head to create theextra shoot.

• Labour input increases by 25%: i.e. there is15% labour increase related to extra stemshandling and 10% increase related to extrapruning and twisting. This amounts to extra75 hours per ha.

• Prune fruit one leaf above the first leaf ofthe “new double head”

Pollination

Numerous studies have shown that bumblebeesor honeybees improve pollination especially thefirst and last sets when pollination of theflowers can be impaired by environmentalconditions. Improved pollination results infaster fruit growth, higher percentage of largeand extra large fruit with thick walls, and loweramount of unmarketable fruit. Effectiveness ofpollinators appears to vary with cultivar.

Honeybees are effective and less expensivethan bumblebees but are a greater nuisance inthe greenhouse. They should be introduced tothe crop three to four weeks prior to flowerdevelopment to aid in acclimatization of thehive. Leasing beehives from an apiarist may bean option. Ensure the hive is supplied with afeed source during the introduction. In order toensure proper colony health, the hive should beinspected at least weekly and the necessarymedicinal supplements added.

Harvesting

From fruit set in early to mid-January until colourripening requires 8 to 10 weeks (depending oncultivar). It takes approximately four weeks frommature green to red, orange or yellow stage ofripeness. Time from fruit set to harvest shortensas the season progresses into the summer months.The last set in early to mid-September takesapproximately 90 days to mature.


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Although it is difficult to achieve, target auniform fruit harvest of 6 to 7 fruits/m2/perweek. Harvesting larger numbers of fruits (10to 13 fruit/m2/week) may cause root diebackand negatively affects plant balance. Fruitflushes also hinder calcium uptake and canresult in BER.

Harvest when fruit is 85 – 90% coloured.Generally, pick one to two times per weekdepending on the week of production andcolours. Peppers should be cooled as soon aspossible and stored at 7 to 8oC and 90% RH.

Use a sharp knife with a blunt end to removethe fruit. This ensures a clean cut, reduces theincidence of stem infection and avoids damag-ing the adjacent fruit. By-pass or scissor prun-ers should be avoided as they leave roughwound sites prone to pathogen infections.

Options for harvesting fruit at the end of theseason include:

• Two weeks before end of the crop, pickgreen fruit, which will not ripen in time forcleanup (providing there is a market forgreen fruit).

• One week before the end of the crop, pickall ripe fruit.

Storage

Peppers are sensitive to low temperatures(>2oC) and low humidity, especially if the fruitis cold-stored and then exposed to temperaturesof 19 to 21oC. Recommended storage tempera-ture for green peppers is 10oC and for coloured,7 to 8oC. Storage temperatures can affect therate of colour development. At 70% colour,yellow peppers take 23 days to reach maturityat 8oC and only 7 days at 24oC; reds take 13and 10 days respectively.

Yellow peppers generally have a low shelf lifeand are more susceptible to moisture loss.Shrink cracks in colored peppers significantlyreduce their shelf life.

Moisture (RH) needs to be added in storagefacilities to prevent fruit desiccation. At lowRH, fruit can lose its firmness (2% moistureloss) or show shriveling (6% moisture loss)within a few days.

Seasonal ManagementStrategiesThe production stages for a pepper crop can besubdivided into a number of growth periods:Winter (December to January); Early Spring(February to April); Late Spring/Summer (Mayto August); and Fall (September to November).Each growth period requires specific manage-ment strategies to maximize yield and plantgrowth. These include: control over the average24-hour temperature (ADT), irrigation (feedand over-drain), carbon dioxide level, vapourpressure deficit (VPD), leaf number, and fruitnumber. The following recommendations areguidelines only. Variations in greenhouse con-struction, seeding date, location, cultivars andpersonal experience influence decisions. Summarytables of each growth period are also provided fora quick checklist of target strategies.


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WINTER PRODUCTION (December/January) to Week 4

maintenance of optimum and uniform tempera-tures is more important than light interception.Screens accelerate fruit production, save energyand can be used to extend the day temperaturetwo to three hours during winter days. Thetemporary overhead screen is used only for thefirst 5 to 6 weeks in order to build a strongvegetative plant. Plants grown under the screenfor too long will stand a greater chance ofpathogen infection and may produce largevegetative flowers that result in low fruitquality. Excessive use of the screen lowersVPD and transpiration rate. It is important tomaintain VPD between 3 to 7 grams/m3 whenusing the screen; vent above the screen ifhumidity control is required.

IrrigationDuring winter production maintain feed EC at3.0 to 3.5 and pH at 6.0 to 6.2. Recommenda-tions for high EC levels are based on plantsreceiving low volumes of feed and sawdust-composting bacteria tying up nutrients. WhenEC of the drain is > 5.0 and pH is > 7.5,reduce feed EC to 2.8 and pH to 5.8.

Irrigation volumes are larger (120 to 150 ml) inthe winter than in the summer (80 to 100 ml).This ensures even feed distribution within thegrowing medium and that drain EC reachestarget levels. Total irrigation in ml/m2/day,should amount to 2.5 times the daily radiation(i.e. 300 joules/cm2/day X 2.5 = 750ml/m2/day). A general guide for watering during winterproduction is based on time: water every 2hours during the day (i.e. 4 times) and every 4-6hours during the night (i.e.twice) if hot heatingpipes (65oC) are used. The over-drain (OD)should be kept between 0 and 5%. As a rule ofthumb, the sum of the feed and drain ECshould total 6.0; e.g. 2.8 EC of feed + 3.2 ECof drain = 6.0 EC total.

CO2

There is little ventilation during winter produc-tion and CO

2 can build up very quickly. Do not

exceed 1000 ppm as higher CO2 levels increase

Temperature and LightWinter production starts by promoting fast andstrong vegetative growth of the 7.5-week-oldseedling prior to the fruit set at early to mid-January. Maintenance of optimum growingconditions during December and Januarydepends mainly on temperature control. Duringthis period, temperature settings are based onlight levels and ADT is adjusted in relation toaccumulated light. In December and January,accumulated light can vary from 50 to 600joules/cm2/day. The average for the twomonths is 250 joules/cm2/day. Frequenttemperature adjustments are required to main-tain balance between production and consump-tion of sugars. Under low light and high tem-perature, consumption of sugars may exceedtheir production; plant growth and fruit qualitycan be compromised.

The rail pipes can be heated to a maximum of65oC to maintain desired air temperature.During snowfall rail pipes may require tempera-tures of 70 to 80oC to melt snow and preventthe greenhouse from collapsing. On clear, coldnights tissue temperatures can drop 5oC belowair temperature even at a maximum pipe tem-perature of 65oC. Increase day temperature tocompensate for lower than targeted nighttemperature.

A combination of rail and grow pipes creates a‘softer’, more uniform climate, which promotesvegetative growth and fruit setting. Locate thegrow pipes away from the plant head duringfruit setting.

Use of a permanent screen or a temporaryoverhead anti-condense polyethylene sheet (20x 20 cm hole spacing) will create more uniformclimate throughout the greenhouse. Withoutthe screen, temperature differences betweenthe growing medium and plant canopy can varyas much as 5 oC. Such a range can negativelyaffect the plant’s ability to set fruit.

Use of screens reduces light intensity in thegreenhouse. During this period, however,


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the risk of flue gas contaminants (e.g. ethylene).The carbon monoxide (CO) reading should be lessthan 2 ppm for acceptable quality of flue CO

2.

Plant and Fruit DevelopmentWinter production starts with promoting strongvegetative growth prior to fruit set in early tomid-January. Establishing a strong plant prior tofruit set ensures a large leaf area (2-3 m2 /m2 offloor area) and abundant assimilate production.Adequate supply of assimilates is an essentialcondition to ensure quality flowers and goodfruit set.

Vigorous vegetative growth can be promoted byfrequent adjustment of ADT based on lightlevels. Excessive vegetative growth should beavoided as it increases the risk of Fusarium

infection and BER. Do not start with plants thatare too young as they tend to be vegetative,especially when growing in sawdust. Flowers areharder to establish in young, vegetative plantsand fruit production is delayed.

Set first fruit as early as possible in January, butonly after the plant has reached 4 to 5 leavesabove the fork. This will ensure the optimalnumber of sets for the season (6 sets/stem).Early fruit set can be encouraged by:

• increasing day/night differences in tempera-ture (night as low as 15oC);

• optimizing light levels by opening the screenduring the day;

• increasing CO2 levels up to 1300 ppm for a

short time;

• increasing irrigation EC up to 4.0;

• lowering the moisture content in the media.

Under limited light conditions it is easier toinitiate fruit set in a small, generative plant thanin a strong, vegetative one. This is probably whyfruit set in strong pepper plants is often delayedto the 5th or 6th week.

Presence of vigorous flower buds bent down-wards 90 o is a good predictor of a successfulfruit set. Lowering of average night and mediatemperatures may be required to improve the

chances of pepper plants producing strongflower buds.

Early setting of 2 to 3 fruits per plant or 1 to 1.2fruits per stem, ensures plant balance and maxi-mum total yield per plant. Do not over-load fruiton the first set because February traditionally haspoor weather and the following fruit sets may becompromised.

Watch head thickness and distance of the flow-ers from the head. Thick heads lead to large,vegetative flowers which produce poor qualityfruit. Higher ADT can correct head imbalance.

Several techniques are used to maintain growthspeed and fruit development. These include:raising temperature, harvesting mature greenfruit, and thinning fruit. Raising the temperatureat the mature green stage accelerates ripeningand helps the ‘swelling’ phase of the remainingfruit. The temperature increase should begradual to avoid a risk of fruit abortion. Har-vesting mature green fruit will induce a newflush of fruit set. Avoid fruit thinning too soonafter fruit set since the energy demand on theplant is relatively low. This may cause the plantto start setting all over again.

Climate Strategies

Promoting Rooting

• For two days after planting, ADT should bekept at 21oC day and night.

• Thereafter target root temperature at 2-3oCbelow air temperature. Ensure that bags arewell drained; the temperature of rootingmedia is between 20oC - 21oC and irrigationwater is over 18oC. This will optimize rooting.Plants should start rooting in 2 to 6 days.

• Maintain uniform rooting conditions through-out the media. Fill the bags with feed solutionfor a few days prior to cutting draining holes.To distribute moisture uniformly, ensure thatthe drainage hole is a vertical 4-5 cm cut onthe side extending to the bottom of the bag.Cut 2-3 slits per bag. Let the roots search for


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water. This process helps build a strong rootsystem throughout the entire growing mediabase. Over-watering, poor profiling andinadequate drainage can create an oxygendeficiency, restricting the growth and distribu-tion of roots.

• Make sure there is good contact between theblock and the media. Irrigate 2.5 times thedaily radiation (i.e. 300 joules/cm2/day X 2.5= 750ml/m2/day) and ensure maximum 5%over-drain.

• Once the plant is anchored, reduce the irriga-tion feed cycle by a third. For example, at 300joules/cm2/day use 500 ml/m2/day. This willaid the roots in spreading uniformly through-out the media in search of moisture.

Promoting Vegetative Growth

Target Temperature• To aid acclimatization of the seedlings in a

greenhouse, keep the average night and daytemperatures within 1 to 2°C. After the plantshave acclimatized, set the temperatures at23oC day and 21oC night.

• Under low light intensity (<100 joules/ cm2/day), reduce the ADT by 0.5 to 1.0oC

• During prolonged low light intensity (<150joules/cm2 /day), typical in December, keepthe ADT at 19.5 to 20.5oC and lower the nighttemperature to 14 to16oC for 4 to 5 days.

• In January when light intensity is high (>200joules/ cm2/day), increase ADT to 20.5 to21.0oC.

• Target to reach day temperature at sunrise byincreasing night temperature at the rate of 1oCper hour.

• Set minimum rail pipe temperature at 45 to50oC; maximum at 65oC.

• If a cold period requires maximum pipetemperature of 65oC but ADT is still belowthe target, compensate by increasing ADTover the next few days.

• If outside temperatures are cold for long

periods, leave the screen closed in order toconserve temperature. Do not open thescreens for light benefit.

• Management of grow pipes:

- with energy screen available, increase growpipe temperature from 40oC to 50oC only iftarget temperatures are not reached.

- without energy screen available, increasegrow pipe temperature to 50oC and aboveonly if target temperatures are not reached.

Target CO2

• Target minimum of 500 to 600 ppm CO2 in

December.

• Avoid CO2 level higher than 1000 ppm,

especially if a temporary screen is used.

• Maintain 500 ppm at night by shutting off theCO

2 supply one to two hours before sunset.

This target is difficult to achieve in the firstmonth of growing because of the CO

2 being

generated from sawdust decomposition.

Target VPD• Maintain VPD at 3 to 7 g/m3. This will en-

hance plant growth and disease resistance.

• VPD exceeding 14 g/m3 for a short time is nota problem, providing the plants are not wilt-ing.

• Maintain VPD higher than 3 when using afixed screen. A small vent opening (0.5 cm)on the leeward side may be required above thescreen.

• To raise VPD:

- Cut holes in the screen for the last 10 daysof use to allow better air exchange between‘attic’ air and that below the wire. Tempera-ture differences created by venting shouldbe minimal to avoid cold air reaching theheads.

- Use vents on a limited basis (<1cm) if theoutside temperature is greater than 7oC andthe radiation is >150 joules/ cm2.


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• At low VPD (<3) avoid day temperaturesbeing reached too early in morning.

Target Irrigation and Feed• Target feed EC 3.0 to 3.5 and pH 6.0 to 6.2.

• Maintain nutrient feed at higher than 18oC. Atemperature difference between the head androots higher than 5oC negatively affects plantgrowth. Water temperatures lower than 18oCalso decrease fertilizer solubility and uptake.

• Target an over-drain of 0 to 5%.

• If pH in the drain is too high, reduce it byincreasing ammonium concentration in thefeed. Avoid use of ammonium when the drainpH is low (5.5), or manganese will exceednormal levels. High pH levels in sawdust (7 to7.2) can be tolerated for short periods, espe-cially in the early stages of rooting.

• Optimal phosphorus levels for this periodare 1.0 to 1.75 millimoles/L. Phosphorusabove or below the recommended range cancompromise flower, fruit and root develop-ment. If you are required to add phosphoricacid to adjust the pH, keep the concentrationof phosphorus below 1.75 millimoles/L. Toohigh levels can cause calcium precipitation atthe drippers and also interfere with magne-sium uptake; too low P can increase inci-dence of BER.

Promoting Fruit Setting

Target Temperature• Target ADT between 19.5 and 21.0oC (17 oC

pre-night for 1.5 to 2.5 hours, 18 to19oCnight, 22oC day). Increase day temperature to23 oC or 24 oC under sunny conditions topromote fruit set.

• Keep moderate temperatures during the firsttwo weeks in January (i.e. 18oC night, 20.5oCday and 22oC afternoon for a short period).Maintenance of such a temperature profilewill improve assimilate allocation to flowersand fruit set.

• Maintain plant growth speed through themaintenance of an active climate (3 to 7

VPD) and target temperatures, especiallywhen natural plant growth slows at the endof January to the beginning of February as aresult of initial fruit set.

• When light levels are low (<150 joules/cm2/day), it may be necessary to use a 14 to 16oCpre-night for 3 to 4 hours to initiate the firstflowers. Use 50oC minimum pipe tempera-ture between 10:00 and 15:00 hour, and ventat 1oC above the set point to encourage airexchange. Avoid limiting maximum ventsetting in the new computer programs. Useoutside temperature and wind speed tomodify (P-band) temperature factor.

• With cold outside temperatures (>0 oC), theuse of maximum pipe temperatures higherthan 65oC may be required to maintain targettemperature. During fruit setting, do notexceed 65 oC even if ADT falls below target.

• Limit the ventilation set point to a maximumof 23 oC to balance fruit development andplant speed. Too high ADT under limitedlight conditions can lead to fruit abortion.

• Once fruit size is large enough to preventabortion (>2 cm in diameter), increase ADTby 1oC. This will maintain growth speed iflight conditions are above average.

• Minimize the use of grow pipes during thecritical fruit setting stage. Higher tissuetemperatures in the head created by growpipes can negatively influence fruit setting,especially under low light conditions.

Target CO2

• In January target 700 ppm CO2 during dark

weather and increase to 1200 ppm duringsunny weather to promote good fruit set.The more frequently the CO

2 system turns

on, the stronger the indication of CO2 use

and the better assurance of fruit set.

Target Irrigation and Feed• Maintain an over-drain (OD) of 0 to 5% in

the 1st irrigation cycle, 25% in the 2nd andup to 50% in the 3rd.


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• Total daily irrigation volume during this timeof the year amounts to 2.5 times radiation(e.g. 300 joules/cm2/day radiation x 2.5factor for peppers = 750 ml/m2/day).

• Under poor conditions for fruit setting,temporarily lower the volume of irrigationand increase EC in the drain. This can aidthe flower setting process.

Target VPD

• Optimal VPD is 3 to 7 g/m3. VPD lowerthan 3 can decrease flower quality.

Plant Management

Leaf Number

• It is important to space young plants uni-formly in the row by aligning vertical stringspacing and tension. This will optimize lightinterception by the plant canopy.

• Prune main stem to one leaf weekly untilfruit development starts. Delaying the proc-ess draws limited carbohydrate reserves fromthe developing plant. Setting fruit reducesshoot development and extends the pruningcycle to 10 days.

Fruit Number

• Remove flowers and fruit buds until the 4th

node (leaf) above the fork as they draw as-similates which should be used for plantgrowth and root development.

• Small generative flowers on the main stemproduce the best quality fruit; avoid second-ary side-shoot flowers that produce lowerquality fruit. In the event of difficult andlimited setting of the main flowers, secondaryflowers can be used for setting. See colourphoto 10.

• The rule of thumb for the optimum numberof fruit per stem for the first set is to dividethe week number in which the fruit set bytwo. Exceptions to the rule are: generativecultivars, three-stem systems and late sowingdates, all of which have less fruit per stemthan the suggested optimum.

• For October seeding dates: It is important toprevent higher than 1.2 fruit/stem. Februaryis historically a dark month and fruit setgreater than 1.2 often reduces growth speed,fruit development, fruit quality and chancesof subsequent fruit setting. A conservativeapproach is to set 1 fruit per stem on the 1st

set, thus encouraging balance and speed andan easier second set. Early production is,however, reduced to approximately 1.4 kg/m2.

• For November seeding dates: Two fruits perstem is equivalent to 2.4 kg/m2. If the fruitloads are too heavy for the light levels andheads begin to thin, reduce the fruit load.Skilled workers can judge individual plantvigor, allowing 2 fruits per stem for strongplants and 1 fruit per stem for weaker plants.

• Excessive fruit load (1st fruit set $ 20/m2) cancause compacting of the head and shorteningof distance between flower and head. Bringthe day and night temperatures closer together(21 to19.5oC), keep the screen closed toincrease RH, prune fruit to 11 fruit/m2, andensure adequate irrigation to correct for anoverly generative plant. When applied gradu-ally, these management techniques will restorebalance between growth and fruit load.

• A high fruit load of uniform size will drawtoo many assimilates at the expense of rootand shoot growth. A moderate set and grada-tion of fruit sizes will allow a more uniformpartitioning of assimilates among the fruit,roots and head.

• When the first fruit set is followed by ex-tended periods of low light intensity, removepart of the set (1.2 fruits/stem) to maintaingrowth speed and plant vigour.

• Remove wings and tails from the fruit as earlyas possible to allow the scars to heal duringearly fruit growth. To avoid leaving a large scar,this should be done only when fruits are firm.

• It takes 8.5 to 10 weeks from flower to har-vest for the first set, depending on fruit load.Beyond this, the longer the fruit remains onthe plant, the greater the risk of poor quality.


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Tab

le 4

-2. W

inte

r p

rod

uct

ion

cyc

le /

Dec

emb

er-J

anu

ary

(up

to

wee

k 4)

G

row

ing

Str

ateg

y 1.

S

tart

: w

ith

a 7

to

7.5

-wee

k-o

ld, c

om

pac

t p

lan

t g

row

n u

nd

er s

up

ple

men

tal l

igh

t (c

a. 4

0 g

ram

s).

2.

Pro

mo

te:

a st

ron

g v

eget

ativ

e g

row

th w

ith

a la

rge

leaf

are

a an

d w

ell d

evel

op

ed r

oo

t sy

stem

th

rou

gh

Dec

emb

er t

o m

id-J

anu

ary.

Set

fru

it in

ear

ly t

o m

id-J

anu

ary

wh

en p

lan

ts h

ave

5 le

aves

pas

t th

e ax

il, o

r in

mid

- to

late

Jan

uar

y w

hen

pla

nts

hav

e 4

leav

es p

ast

the

axil.

3.

Fin

ish

: w

ith

7-1

0 fr

uit

/m2 b

y th

e en

d o

f Ja

nu

ary.

Gro

wth

S

tag

e T

emp

erat

ure

(oC

) C

O2

(pp

m)

VP

D (

gra

ms/

m3 )

and

Ven

tila

tio

n

Irri

gat

ion

P

lan

t M

anag

emen

t

Rooting

Set

24h

r at

21o

Med

ia a

t 20-

21o

Irrig

atio

n at

tem

pera

ture

hig

her

than

18o

Use

500

–70

0, li

quid

gas

pr

efer

red.

Sta

rt a

t sun

rise,

sto

p 1-

2 ho

urs

befo

re s

unse

t

Tar

get V

PD

3 -

7

Pre

-cha

rge

bags

with

nut

rient

so

lutio

n at

tem

pera

ture

hig

her

than

18o C

Sta

rt 2

hou

rs a

fter

sunr

ise,

sto

p 2

hour

s be

fore

sun

set

Pla

nt h

eigh

t 60

- 75

cm

tall

Wei

ght h

ighe

r th

an 4

0g/p

lant

Vegetative Growth

Set

24h

r at

20.

5o with

a d

ay u

p to

23o , n

ight

19

- 20

o

If lig

ht is

less

than

200

J/cm

2 /d

ay, s

et a

t 19.

5 to

20.

5o

If lig

ht is

mor

e th

an 2

00

J/cm

2 /day

, set

at 2

0.5

to 2

1.0o

Min

imum

rai

l pip

e at

45

to 5

0o , m

axim

um a

t 65o

Use

700

to m

ax 1

000,

boi

ler

gase

s

If lig

ht is

less

than

200

J/c

m2

/day

for

a fe

w d

ays,

red

uce

to

500

- 70

0

Shu

t off

CO

2 do

sing

ear

ly in

p.

m. t

o re

duce

nig

ht le

vels

ge

nera

ted

from

saw

dust

Less

than

1 c

m v

entin

g m

ay b

e ne

eded

to r

educ

e ni

ght l

evel

s be

low

500

Tar

get V

PD

3 -

7

Ven

t on

lee

side

le

ss th

an 1

cm

ab

ove

scre

en if

V

PD

is le

ss th

an 3

an

d on

ly w

hen

outs

ide

is h

ighe

r th

an 0

o C

Tot

al w

ater

ing

2.5

times

ra

diat

ion

EC

feed

3.5

; pH

6.0

EC

dra

in 2

.5-4

.0; p

H 5

.8 –

6.8

Tim

e 1.

5 -

2 ho

urs

or e

very

80

- 90

joul

es/c

m2

Vol

ume

120

- 15

0 m

l

1 or

2 n

ight

wat

erin

gs

depe

ndin

g on

pip

e te

mp.

If

%O

D >

10%

, dis

cont

inue

Pru

ne to

1 le

af e

very

10

days

Do

not p

rune

abo

ve 1

0 cm

bel

ow

the

head

Allo

w to

set

onl

y 4

- 5

leav

es p

ast

the

fork

Dur

ing

prol

onge

d da

rk w

eath

er,

rem

ove

gree

n fr

uit t

o 1

- 1.

2/st

em

Fruit Set

Set

16o -

18o p

re-n

ight

for

frui

t se

tting

U

se 7

00 to

max

100

0

Goo

d qu

ality

ge

nera

tive

flow

ers

are

prod

uced

whe

n V

PD

> 3

EC

feed

3.0

- 2

.5; p

H fe

ed 5

.8.

EC

dra

in 4

.0; p

H d

rain

6.0

-6.8

OD

-5%

1st s

et, O

D 2

5-35

% 2

nd

set

Vol

ume

80-1

20 m

l

Tar

get s

tem

flow

ers

rath

er th

an

side

sho

ot fl

ower

s

Ear

ly s

et 1

.2 fr

uit/s

tem

, mid

-late

hi

gher

or

equa

l tha

n 2

Rem

ove

defo

rmed

or

crow

ded

frui

t in

exce

ss o

f 2/s

tem

Bio

log

ical

Co

ntr

ol

Dis

ease

s an

d P

hys

iolo

gic

al D

iso

rder

s

Pro

pag

atio

n

Mon

itorin

g pe

sts

Intr

oduc

e pr

even

tive

mea

sure

of H

ypoa

spis

spp

. and

A. c

ucum

eris

and

ot

hers

if n

eces

sary

T

rans

fer

the

info

rmat

ion

on th

e pe

st s

tatu

s to

the

grow

er

On

ce t

he

pla

nts

are

in t

he

gre

enh

ou

se c

on

tin

ue

mo

nit

ori

ng

an

d e

stab

lish

p

reve

nti

ve c

on

tro

l fo

r:

Thr

ips:

A. c

ucum

eris

F

ungu

s gn

ats:

Hyp

oasp

is s

pp,

Aph

ids:

ban

ker

plan

ts w

ith A

phid

ius

spp.

S

pide

r M

ites:

Sta

rt c

urat

ive

and

prev

entiv

e in

trod

uctio

n of

P. p

ersi

mili

s at

the

first

si

gn o

f inf

esta

tion

Loop

ers:

pla

ce p

hero

mon

e tr

aps

to m

onito

r th

eir

pres

ence

D

o no

t int

rodu

ce d

iapa

usin

g bi

o-co

ntro

l age

nts

Dis

ease

s

Rem

ove

and

repl

ace

plan

ts w

ith s

tunt

ed o

r ab

norm

al le

af g

row

th. T

est t

he p

lant

s fo

r po

ssib

le P

eppe

r M

ild M

ottle

Viru

s.

Wat

ch f

or

sym

pto

ms:

Dis

tort

ed le

af g

row

th in

the

head

plu

s th

e pr

esen

ce o

f thr

ips

–

poss

ible

Tom

ato

Spo

tted

Wilt

Viru

s.

Bas

al s

tem

dis

colo

ratio

n -

Fus

ariu

m c

row

n ro

t. R

hizo

pus,

Erw

inia

on

frui

t.

Ph

ysio

log

ical

Fru

it D

iso

rder

s

Wat

ch fo

r cu

ticle

cra

ckin

g, w

ings

, tai

ls, i

nter

nal g

row

ths.


4.

Pep

per

Pro

du

cti

on

SPRING PRODUCTION (February/March/April) Weeks 5 – 18

levels at night. Frequency and degree of ventopening depends on outside conditions.

IrrigationDuring spring production radiation levels areinconsistent and irrigation volumes are stillrelatively low (< 5 L/m2), therefore the EC ofthe feed is allowed to fluctuate between 2.5 and3.0. Typically EC decreases with increasing lightintensity and volume of irrigation cycles. At lowlight intensity a higher EC is needed to meet thenutritional demand for growth and fruit develop-ment. Adjustments in EC levels should beimplemented gradually as abrupt changes in ECcan cause root damage and slow growth. Extrairrigation cycles may be required during rapidfruit development.

As in winter total irrigation is calculated at 2.5 to3 times the radiation level but the start and stopirrigation times are different. Irrigation starts 1.5to 2 hours after sunrise and stops 1.5 to 2 hoursbefore sunset to reflect the increasing intensityand duration of light. Correspondingly, irrigationvolumes are reduced from between 120 and150ml/cycle to between 100 and120ml/cycle. Itis during this period that the percentage of over-drain (OD) increases (25% for the 2nd fruit setand up to 50% for the 3rd fruit set) and re-circulation begins. The first OD is required bythe second irrigation cycle in order to refresh andlower EC and restore moisture in the media. Theinterval between subsequent irrigation cycles canincrease.

In transition weather (bright to dark), use lessfrequent cycles. They will provide a more uni-form EC and pH in the media. Stop the lastirrigation cycle earlier to allow the media to drydown. Less frequent cycles, along with driermedia by the end of the day, will keep the rootsactive and reduce the risk of BER.

CO2

In spring plants use more CO2 than in winter.

The higher consumption of CO2 is due to in-

creasing uptake by plants and venting losses to

Temperature, Light and VentilationBy this time plants have been growing for twomonths; the first set is established and thesecond set is being initiated. Maintaining bal-ance between growth speed and fruit load is themain issue. Optimum growing conditions fromFebruary to April are maintained by controllingtemperature, VPD, CO

2 and irrigation.

During this period intensity and duration oflight increase progressively. Accumulated lightlevels range from 540 to 1800 joules/cm2/day.Minimum light levels required for maintainingplant growth range from 150 to 300 joules/cm2/day. To ensure the quality of flower budsand fruit set, the plant must produce a surplusof energy, which requires light levels higherthan the minimum. An energy shortage duringfruit development may cause growth to stag-nate and roots to die-back.

As in winter, temperature settings are based onlight levels to maintain balance between produc-tion and consumption of assimilates. ADT isstrongly influenced by radiation, especially as itrelates to daytime temperatures. The minimumnight temperature can be set low (e.g. 16oC)providing that day temperature compensates.

The rail pipes are still essential for control oftemperature but there is increasing reliance onlight levels for temperature control. Lightintensity higher than 300 watt/m2 is the thresh-old above which the minimum pipe is removed.

ADT can also be adjusted with the use of “pre-night” temperatures. It is a particularly usefulmethod when large temperature differences areneeded between the day and night to promoteflower initiation.

During February and March and at outsidetemperatures below 8oC, condensation of watervapour on the glass removes 0.8 to 1.0 L/m2 /day of water from the greenhouse air. It is notuntil late April that ventilation consistentlyplays a significant role in climate control. It isused to reduce temperature, humidity and CO

2


4.

Pep

per

Pro

du

cti

on

the outside. It is important to monitor and adjustdaily targets of CO

2 levels.

Plant and Fruit DevelopmentAs emphasized earlier the pepper plant sets fruitonly when assimilate supply exceeds demand.Light levels are critical for fruit set and develop-ment. Optimize light levels by reducing the useof movable screens during fruit set, especiallyunder low light intensity. Movable screens canreduce light transmission by 20 to 40%.

Size of the second set influences ongoing bal-ance of the plant through the rest of its produc-tion cycle. A small second set can lead to anoverly vegetative plant with strong head andstrong vegetative flowers. By contrast, a largesecond set will slow the plant’s growth.

Different stages of fruit development requirevarying amounts of energy (assimilates) from theplant. For example, newly set fruit or colourdevelopment in mature fruit demands a rela-tively small amount of energy compared to thedemands of the mature green stage. A range offruit stages on a plant ensures uniform partition-ing of assimilates among the developing fruit,roots and head.

Throughout the spring period, build a strong andvigorous plant with abundant leaf area and well-matted root system. These characters are criticalfor maintaining optimum fruit production duringthe summer.

Climate Strategies forVegetative Growth and Fruit Set

Target Temperatures• ADT can range from 20 to 23oC depending on

light levels, fruit set and fruit size.

• Increase ADT at the beginning of the secondset (week 7) to stimulate development of thefirst set.

• Under low light (<100 joules/cm2/day), keepADT above 20oC to maintain plant growthspeed.

• Under extended periods of dull weather, drop

ADT to 19.5 to19.8oC and provide mid-dayboost.

• Target ADT of 21 to 22oC during fruit setting.

• Maintain growth speed by increasing nighttemperature from 18 – 19oC once the fruitexceeds 40 mm in diameter.

• Use the length of the pre-night temperaturerather than the lowest temperature at night asa means of controlling ADT.

• It is important to meet day temperatures justprior to or at sunrise. Target day settings justbefore sunset to build up a higher RH in thegreenhouse.

• Maintain climate conditions favouring thedevelopment of small generative flowers (i.e.a large difference between day and nighttemperatures). These produce thick-walledheavy fruit.

• Once 60% of flowers are set, remove the pre-night temperature control.

• During transition weather from <500 joules/cm2 to > 2000 joules/cm2, use screens toprotect the fruit from sunscald.

Pipe Management• Run a minimum rail pipe temperature of 40oC

and maximum of 65oC.

• Use ADT of 23oC and provide a rail pipe of50 to 55oC between 10:00 to 15:00 hours toprovide a temperature boost to promotegrowth. This is especially important withstrong crops.

• Light level above 300 watts/m2 is the thresh-old to start venting and discontinue minimumpipe temperature.

Target C02

• Maintain CO2 levels at 700 to 1000 ppm from

one hour after sunrise until one hour beforesunset.

• Higher than 1000 ppm of CO2 can reduce

leaf size and cause yellowing of leaves.


4.

Pep

per

Pro

du

cti

on

• Reduce CO2 levels during transition weather

(dark to bright). Under such conditions highlevels of CO

2 can cause tissue damage.

• Sawdust and soil on the floor area can gener-ate high levels of CO

2 (>1000 ppm) during

the night. Turn off CO2 dosing 2 hours before

sunset and vent slightly to keep the CO2

levels below 500 ppm.

• CO2 levels can be used as a tool to direct the

crop in a vegetative or generative direction.CO

2 concentrations of 700 to 1300 ppm

supplied for a short period can provide agenerative signal to the plant.

Target VPD• Target 3.0 to 7.0 VPD with 4.0 before mid-

day and from 3.0 to 3.5 in afternoon.

• During hot weather, activate the plant early inthe morning using a minimum pipe. This willincrease the RH in the greenhouse and allowplants to cope better with the stress related tothe high temperatures in the afternoon.

• Use a maximum vent followed by roof sprin-klers if VPD is higher than 7.0 or insidetemperature exceeds 28oC and the plant isshowing wilt stress.

Target Ventilation• Start ventilating during bright days when the

outside temperature is above 8oC and there islittle chance of cold air chilling the plant heads.Start with the lee side and use the wind sideonly when wind speed is less than 2m/sec.

• Use a large dead zone and very reactive p-band in the early part of the spring period.

• Vent when temperatures inside the green-house reach 24oC and outside temperaturesare higher than 8oC. New, tightly-sealedhouses may require a slight vent opening (1 -2 cm) on the lee side when outside tempera-tures are close to 0oC to avoid low VPD.

• A small vent opening (1 to 2 cm) especiallyin morning will aid in controlling humidity.

Be aware of and avoid condensation as asudden drop in air temperature can result incondensation on fruits and plant tissue.

Target Irrigation and Feed

EC targets

• Target feed EC of 2.5 to 3.0 until the end ofApril.

• During cloudy weather increase EC up to 3.2.

• If the plant is too vegetative, increase EC.

• Target drain EC of 2.8 to 3.5.

pH targets

• Target feed pH of 5.8 to 6.2.

• Target drain pH of 6.5 to 6.8.

• Feed pH lower than 5.5 will damagerockwool fibers.

• pH in sawdust bags can be lowered by using0.5 to 1 mmol/L ammonium in the feed.

Note: the incidence of BER may increasewhen using high levels of ammonium.

Nutrient targets

• Buffer water with bicarbonate (sodiumbicarbonate or potassium bicarbonate) ifwater source contains less than 50 ppmbicarbonates. Introduce the bicarbonates in aday storage tank prior to mixing in the con-centrate from A and B tanks. Ideally, thebicarbonates need 12 to 24 hours to reachchemical stability.

• Follow general feeding guidelines adjustedfor over-drain analysis; note differencesbetween start, picking and high volumeformulas (see Table 3-15, page 39).

• When re-circulating nutrient solution, blendone part of the old solution with two partsof the new solution in order to avoid nutri-ent imbalances.


4.

Pep

per

Pro

du

cti

on

• In re-circulated solution, target:

- chloride (Cl-) of 1 to 3 mmol/L;

- sodium (Na+) of below 6 mmol/L.

Volume and over-drain targets

• Target irrigation volume (ml/m2/day) ap-proximately 2.5 times the value of accumu-lated light.

• Start irrigating 1.5 to 2 hours after sunriseand stop 1.5 hours before sunset.

• Feed from 120 to 150 ml/m2 / cycle untilMarch, then reduce it to between 100 and120 ml/cycle.

• If a night watering is required, 80 ml/cycle issufficient.

• It is important not to over-wet the sawdustor rockwool when ADT is at 25oC or above.Under these conditions, oxygen concentra-tion in the feed solutions and growing mediabecomes limited and roots may be damaged.

• During bright weather, target first over-drainby the 3rd irrigation of the morning at 25 to30%.

• During dark weather, target OD of 15 to 20%.

Plant Management

Leaf Number• In March start leaving two leaves per shoot

for generative cultivars or low densityplantings. Increased canopy protects fruitfrom sunscald and provides better coolingthrough transpiration.

• Cultivars like Eagle, with thin canopiesrequire two leaves per shoot starting in mid-February. Prune extra flowers.

• Maintain a 10-day pruning cycle and removeonly leaves 10cm below the head.

• Alternate row pruning cycles to reduce plantstress and its indirect effect on climate.

Fruit Number• Accumulated light and size of first set deter-

mines the timing and success of the secondset. Under low light levels, reduce nighttemperature but elevate day temperature topromote strong flower buds. Lowering ADTis counter productive. It slows the ripeningof the first set and has no effect on initiatingthe second one.

• Maintain more fruits on a vegetative plantand less on a generative one to conditionplants for the approach of summer.

• Target 35 to 40 fruit/m2 for most cultivars,with 30 fruit/m2 for large-fruited cultivarslike 444.

• Use 1 to 2 hour pre-night temperature of 16to 18oC to bend flowers downward.

• During pruning avoid brushing the flowersand small fruit with twine. This could resultin ‘stitching’ or scarring as the fruit enlarges.Generative plants tend to set fruit high,increasing the incidence of sunscald. Keepextra leaves to protect the fruit and use roofsprinklers, white wash or movable screens intransition weather or when the temperatureis higher than 28oC.

Fruit Nutrition• Fruit loads can be very high in April and can

slow down the vegetative growth of theplant. Under conditions of slow vegetativegrowth, the incidence of BER increases.Ensure adequate calcium levels (add 1milli-mole/L) and maintain an active climate.

• Ammonium-free calcium nitrate and pH 6 to6.2 of the feed will also aid the uptake ofcalcium.

• High sodium (Na) as indicated by >12mmol/L in the drain, significantly reducesfruit number and interferes with theK:Ca:Mg ratio and uptake of individual ions.


4.

Pep

per

Pro

du

cti

on

Tab

le 4

-3. E

arly

sp

rin

g p

rod

uct

ion

/Feb

ruar

y-M

arch

-Ap

ril (

wee

ks 5

– 1

8)

Gro

win

g S

trat

egy

1.

Sta

rt: w

ith a

ppro

xim

atel

y 15

-wee

k-ol

d pl

ants

that

hav

e th

e fir

st s

et e

stab

lishe

d an

d th

e se

cond

initi

ated

. P

rom

ote:

a b

alan

ce b

etw

een

the

grow

th s

peed

and

the

frui

t loa

d. B

uild

a s

tron

g an

d vi

goro

us p

lant

with

abu

ndan

t lea

f are

a an

d w

ell-m

atte

d ro

ot s

yste

m.

The

se p

lant

cha

ract

eris

tics

will

be

criti

cal f

or m

aint

aini

ng th

e op

timum

frui

t pro

duct

ion

durin

g th

e su

mm

er p

erio

d.

3.

Fin

ish:

with

>25

frui

t /m

2 by

the

end

of A

pril.

G

row

th s

tag

e T

emp

erat

ure

(oC

) C

O2

(pp

m)

VP

D (

gra

ms/

m3 )

and

V

enti

lati

on

Ir

rig

atio

n

Pla

nt

Man

agem

ent

Vegetative growth

Set

AD

T 2

0o and

23o ,

depe

ndin

g on

ligh

t int

ensi

ty,

frui

t set

or

size

Lo

wer

to 2

0o dur

ing

exte

nded

per

iods

of d

ark

wea

ther

U

se p

re-n

ight

leng

th to

co

ntro

l AD

T

Set

min

imum

rai

l pip

e at

40

, m

axim

um a

t 65o

Rem

ove

min

imum

pip

e at

lig

ht in

tens

ity h

ighe

r th

an

300

w/m

2

Sta

rt 1

hou

r af

ter

sunr

ise,

st

op 1

-2 h

ours

bef

ore

suns

et

Mai

ntai

n 70

0 –1

000

du

ring

day

and

low

er th

an

500

at n

ight

Lo

wer

CO

2 co

ncen

trat

ion

durin

g tr

ansi

tion

wea

ther

Tar

get V

PD

3 –

7 w

ith 4

V

PD

bef

ore

mid

-day

an

d 3.

0 to

3.5

bef

ore

the

afte

rnoo

n S

tart

ven

ting

durin

g br

ight

(>3

00 w

/m2 )

and

war

m d

ays

(>8o C

) or

w

hen

insi

de

tem

pera

ture

is h

ighe

r th

an 2

4o CU

se a

sm

all d

ead

zone

(0

.5 –

1.0)

and

ver

y re

activ

e p-

band

Sta

rt 1

.5 –

2 ho

urs

befo

re

sunr

ise,

sto

p 1.

5 ho

urs

befo

re

suns

et

Tar

get f

eed

volu

me

2.5

times

ac

cum

ulat

ed li

ght m

2 /day

R

educ

e cy

cle

volu

me

to 1

00-

120

ml i

n A

pril

U

se 8

0 m

l for

nig

ht w

ater

ing

Fee

d E

C 2

.5 to

3.0

; pH

5.8

to

6.2

Dra

in E

C 2

.8 to

3.5

; pH

6.5

to

6.8

OD

25-

30%

by

the

3rd ir

rigat

ion

Pru

ne to

1 le

af/s

hoot

eve

ry 1

0 da

ys

Sta

rtin

g in

Mar

ch p

rune

to 2

le

aves

/sho

ot

Do

not p

rune

abo

ve 1

0 cm

be

low

the

head

A

ltern

ate

row

pru

ning

cyc

le

Fruit set or development

Kee

p a

larg

e di

ffere

nce

betw

een

nigh

t and

day

. Thi

s w

ill p

rodu

ce a

thic

k w

alle

d fr

uit

If re

quire

d, u

se 1

-2 h

r pr

e-ni

ght t

o be

nd th

e flo

wer

s do

wnw

ard

Rem

ove

pre-

nigh

t whe

n 60

% o

f flo

wer

s ar

e se

t

Use

700

to 1

300

for

a sh

ort p

erio

d to

stim

ulat

e fr

uit s

ettin

g

Tar

get V

PD

3 -

7

If

requ

ired,

incr

ease

feed

EC

to

pro

mot

e fr

uit s

ettin

g

Tar

get 3

5 to

40

frui

t/m2 o

r 25

fr

uit/m

2 for

culti

vars

with

larg

e fr

uit (

444)

A

void

bru

shin

g th

e flo

wer

s or

sm

all f

ruit

with

the

twin

e. T

his

will

res

ult i

n fr

uit s

carin

g.

Rem

ove

extr

a flo

wer

s

Bio

log

ical

Co

ntr

ol

Dis

ease

s an

d P

hys

iolo

gic

al D

iso

rder

s

Est

ablis

h b

io-c

on

tro

l ag

ents

fo

r:

T

hrip

s: A

. cuc

umer

is ,

Oriu

s.

Fun

gus

gnat

s: H

ypoa

spis

.

Aph

ids:

ban

ker

plan

ts w

ith A

phid

ius

and

rele

ase

Aph

idol

etes

. S

pide

r M

ites:

Sta

rt c

urat

ive

and

prev

entiv

e in

trod

uctio

n of

P. p

ersi

mili

s at

th

e fis

t sig

n of

infe

stat

ion.

Est

ablis

h pr

even

tive

cont

rol w

ith F

eltie

lla

Ste

thor

us, a

nd A

mbl

ysei

us.

Lo

oper

s: E

stab

lish

Pod

isus

, Tric

hogr

amm

a a

nd C

orte

sia.

Dis

ease

s

W

atch

for

sym

ptom

s:

Bas

al s

tem

dis

colo

ratio

n -

Fus

ariu

m c

row

n ro

t.

Sof

t rot

on

frui

t - R

hizo

pus,

Erw

inia

.

Ph

ysio

log

ical

Fru

it D

iso

rder

s

Wat

ch fo

r cu

ticle

cra

ckin

g, w

ings

, tai

ls, i

nter

nal g

row

ths

and

mis

shap

en fr

uit.


4.

Pep

per

Pro

du

cti

on

SPRING-SUMMER PRODUCTION (May to August) Weeks 19 - 35

Light, Temperature and VentilationMaintaining balance between speed of growthand fruit load is of key importance. Duringspring-summer light levels range from 1100 to2700 joules/cm2 /day with monthly averagesclose to 1900 joules/cm2/day, outdoor tem-peratures are high and RH low. Developingfruit must be protected from the high radiationby canopy shading, irrigation and use ofscreens. A full canopy will not only shade thefruit but will also provide abundant transpira-tion to cool the crop during summer heat. Inthe summer, the pepper plant has a tendency tobe generative. Effective climate managementwill ensure balance between growth and fruitproduction.

During this period temperature and RH greatlyinfluence growth and fruit development. Railpipes and venting are the major tools in con-trolling the temperature. The rail pipes are usedmainly during the night and for plant activationin the morning. Pre-night temperatures, screensand rooftop sprinklers are frequently used tocontrol temperature during this period.

Venting is used continuously throughout theday and becomes the most important tool fortemperature control during the summer. Skillfulventing throughout the day has a significantinfluence on total yield. Over-use of vents canresult in excessive transpiration and reducedspeed of growth. Reduction of venting at theend of the day (<108 joules/cm2 /day) is animportant strategy for improving VPD andmaintaining optimum CO

2 levels.

IrrigationDuring this period transpiration often exceedswater uptake. If this is not compensated forthroughout the day, excessive transpiration canlead to accumulated water stress for the plant.

By mid-summer fruit counts per m2 are reachingtheir peak. This period of fruit developmentcoincides with increased sensitivity to BER.Irrigation capacity should be maintained at 1.4

liters/m2/hour (6 to 7 irrigation cycles/hour) toaccommodate maximum transpiration andnutritional requirements of developing fruit.

Extra irrigation cycles may be required underhigh fruit loads (> 25 fruit/m2) and/or whenEC in the media increases. In either case,extending the watering later into the day maybe required to meet the plant needs. Well-managed irrigation will show a tendency forover-drain to increase until 15:00 and declinethereafter.

In re-circulation systems, it is recommended touse 50 to 70% new feed and 30 to 50% re-circulated feed. For example, if the feed EC is2.5 then use 0.75-1.25 EC of re-circulatedfeed and 1.25-1.75 EC of new feed. Usinghigher than 70% re-circulated feed will createnutrient imbalances and can lead to chlorosisand possibly death of the head.

In extreme summer conditions, salt concentra-tion in the slab can be reduced temporarily byirrigating plants with an EC below 2.0 for ashort period of time or by increasing the over-drain above 35%. Such a strategy, however,can damage roots by decreasing their ability toabsorb nutrients and consequently EC willincrease just as fast. Damage to roots has along-term negative effect on plant growth.

By late summer the light intensity declines andplants need less water, despite air temperaturestill being high. Stop irrigating earlier in theafternoon (e.g. 17:30) but maintain the targetover-drain.

CO2

Ensure the CO2 distribution tube is placed

approximately 75 cm under the top of the headduring the spring/summer period to optimizeCO

2 uptake. The concentration of CO

2 during

the day is related to vent management. Ingeneral, CO

2 is optimized in the morning for as

long as possible until venting losses becometoo high (>20% vent). Maintaining dailytargets of CO

2 at 25 kg/1000m2/hour requires


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23oC. Use 23oC for stronger crops and >21oCfor weaker crops.

• Healthy and vegetative crops can tolerate anincrease of 2-3oC above the ADT target of23oC. Temperature of 26-27oC in the after-noon along with optimum RH (80%) andCO

2 (500-700 ppm) promotes growth and

formation of strong flowers.

Maintain pre-night temperature of 15oC until2:00 am and pipe at 25 to 30oC.

Target a night temperature of 20oC by 5:00 am.

• Generative crops with flowers close to thehead will perform better at 23-24oC by lateafternoon. It may be necessary to vent atsunset to reduce temperature.

• When outside temperature is higher than25oC: maintain as cool temperature as possi-ble in the morning. At the same time, acti-vate the plant with pipes (45-50oC). Increasetissue temperature up to daytime tempera-ture 1 to 2 hours before sunrise.

Keep the minimum night temperature at14oC. It will take too long to warm the fruitto the daytime temperature when the nighttemperature drops below 14oC.

• On clear nights maintain night temperatures1-2oC degrees higher than the night tempera-ture target.

• Use roof sprinklers, white wash or fog whentemperature is higher than 27oC and lighthigher than 800 watts/m2. This can reducethe temperature by 2oC. Sprinklers and fogare used typically at mid-day or when theleaves on the head are flagging.

Pipe Management:• Set the minimum pipe temperature at 50oC

by 5:00 am and drop the pipe to 40oC whenlight intensity reaches 300 watts/m2 or onehour after sunrise. When the canopy is full,keep minimum pipe of at least 38 to 40oC toensure good air circulation. The occurrence

continuous monitoring and adjustments. KeepCO

2 at 350 to 400 ppm during full venting. At

the end of the day (<300 watts/m2) and duringrestricted venting, CO

2 can be increased up to

1000 ppm.

High levels of CO2 (up to 1300 ppm) applied

for a short period of time can improve flowerinitiation, while low levels applied at the endof day under reduced venting can promotevegetative growth.

Too high CO2 concentration can cause reduc-

tion in stomatal opening. Keep CO2 <450 ppm

during the highest temperature period (13:00 to17:00 hrs) to maintain optimum transpiration.Too high CO

2 combined with high radiation

can cause discoloration of leaves (grey-yellow),similar to boron deficiency.

In transition weather (cloudy to sunny) andwhen the plant is too generative, maintain CO

2

levels below 450 ppm. Similarly, CO2 levels

should be less than 450 ppm when high radia-tion is combined with high moisture deficit.

Plant and Fruit DevelopmentPruning management depends on cultivar,growth speed, fruit load and other factors.During the summer, leaf pruning is typicallyreduced as more leaves protect developing fruitfrom sunscald and provide better cooling. Hightranspiration rates improve RH in the green-house climate.

Keeping the balance between growth speedand fruit load is the primary challenge duringsummer production. Plants with too high fruitloads will compromise the growth speed andthe fruit will have a higher chance of develop-ing BER. With too low fruit loads, the planthas a tendency to be vegetative and will lose itsyield potential.

Climate Strategies forVegetative Growth and FruitSet

Target TemperaturesADT for this growing period ranges from 22 to


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of dull fruit is often related to the lack ofgood air circulation.

• Drop the pipe temperature to 30oC between19:00 and 23:00 for 2 to 3 hours in order toreduce temperature. From an economic pointof view, turning off the pipe completely isinefficient since it requires more energy toreheat the water than to maintain it at 30oCor higher.

• Use the grow pipe when the canopy is fulland when the light is higher than 300 watts/m2 in order to maintain air circulation. Thisimproves climate in mid-canopy.

VentilationVentilation strategy depends on outside tem-perature and wind.

• When outside temperature is lower than 8oC:

Set dead-zone at 1 to 2oC higher than the airtemperature along with slow acting p-band.This setting will prevent too much cold airfrom coming into the greenhouse.

• When outside temperature is higher than 12oC:

Set dead-zone at 0.5oC higher or equal with afast reacting p-band.

• When outside temperature is expected to behigher than 25oC:

Set the vent settings to depend on lightrather than temperature. Start venting withthe lee side (100%) when light intensityreaches 300 watts/m2. Open the wind sidewhen temperature increases 2o above that ofthe light threshold. Such a venting strategywill conserve RH and prevent temperatureand VPD from rising too fast before mid-day.After 13:00, the climate can be adjustedbased on crop strength, radiation and windspeed. When wind speed is < 1m/sec, windand lee side vents can be opened evenly; at> 1m/sec, delay opening wind side; at >3m/sec, limit wind side opening.

• During summer, venting between 23:00 –9:00 hours becomes the best assurance oflowering the ADT. The night temperaturecan be set at 12oC. Although unrealistic, itwill keep the temperature within target. Lownight temperature will optimize fruit size.

• Rate of temperature dropping to reach nighttime set point:

Outside evening temperatures between 10to16oC; 1oC drop every 30 minutes.

Outside evening temperature higher than16oC; cooling rates can be faster than 1oCevery 30 minutes. The target air temperaturecan be reached within 2 to 3 hours. It maytake 5 to 6 hours to reach the target planttissue temperature.

Screen Management• In transition and hot weather (>800 watts/

m2), use sunscreens to protect fruit fromsunscald and help plant acclimatization.

• Use screens (2/3 open) during hot weather,especially when there is a high percentage ofsmall fruit (20 mm) or the crop is generativewith many flowers. Screens will shade ex-posed fruit, reduce BER occurence andlower leaf and fruit temperature. Leave 30%of the greenhouse unscreened to maintainactive climate.

Target C02

• Target 20 to 25 kg/1000 m2/hour as higherCO

2 levels aid in flower setting.

• Adjust CO2 levels according to temperature

when vents are 35 to 40% opened:< 25oC, maintain 700 to 800 ppm;> 25oC, maintain 350 to 400 ppm.

• Maintain 800 to 1000 ppm during late after-noon (< 300 watts/m2) to sunset with lessthan 20% vents opened.


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EC

• Maintain feed EC at 2.5 to 3.0 and drain ECat 2.8 to 3.5.

• Reduce EC with an increasing light intensityby dropping 0.1 EC at 108 joules/cm2, to 0.4EC at 180 joules/cm2.

• During extended hot periods increase thedrip EC from 2.8 to 3.0 provided the plantsare not flagging and OD is within targetedrange. The increased EC provides a moreuniform osmotic pressure throughout theplant. Reduce EC slightly during the bright-est period of day but ensure EC comes upagain before sunset so that average feedingsare at target EC.

• When EC of the feed is reduced from 2.7 to2.2, micronutrient levels are reduced by25%. Increase micronutrients by 25% whenreducing EC of the feed in order to maintainacceptable shelf life of the fruit.

pH

• Target pH in the feed between 5.8 and 6.2.

• Target pH in the drain between 6.5 and 6.8.

• If pH is higher than 6.5 in the drain, usesolid calcium nitrate with 1% ammonium,ammonium nitrate or urea.

• If pH is between 6.2 and 6.5 in the drain,remove the ammonium nitrate and the ureabut use a reduced amount of solid calciumnitrate with 1% ammonium.

• If pH < 6.0 in the drain, remove all ammo-nium sources and use the liquid calciumnitrate only.

Over-drain

• In July typical use includes 7 L of feed perm2/day or more with target OD at 30%.Higher than targeted OD, especially in re-circulation systems, can cause root problemsrelated to lack of oxygen. Elevated watertemperatures can also reduce the oxygen level.

Frequency of irrigation

• At light intensities between 1350 and 1620joules/cm2, use 3 to 4 irrigation cycles perhour, with 80mL per cycle.

• At light intensity higher than 1890 joules/cm2, use 5 to 6 cycles per hour. Time or lightbased cycles should be verified by the over-drain percentage.

• During peak light hours (11:00 to 16:00),irrigate every 65 to 70 accumulated jouleswith 80 mL per cycle. After 16:00 hours, use100 to 120 mL.

• On sunny days, apply the last cycle at sunset.On dark days, apply it 2 to 3 hours beforesunset. If required, adjust to satisfy over-drain targets.

• Avoid irrigating plants too early; it may causehigh root pressure and fruit cracking.

• Irrigation after 16:00 depends on the cropcondition, climate and fruit load. For exam-ple, provide extra irrigation cycles whenpromoting vegetative growth with highertemperatures, RH, and CO

2 during late

afternoon.

Target nutrition

• The ratio of K:Ca should be close to 1:1.

· K and NO3 have a wide optimal concentra-

tion range but P has a narrow one. Concen-tration of P below recommended levelscould increase the chance of BER incidenceas Ca uptake is proportional to P level.

• Plant uptake of Na, Cl and SO4 ions is

limited and they tend to accumulate in thenutrient solution, particularly in a re-circula-tion system. Monitor concentration of theseions carefully.

• The optimum concentration ranges formicro-elements are quite narrow; deficiencyor toxicity is easily triggered.

• Too high levels of ammonium (>1 mmol/L)and poor pH control can lead to high inci-dence of BER.


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Plant Management

Target Leaf Number

• Prune to two leaves depending on fruitexposure, especially plants in edge rows.

• Avoid twisting and removing shoots duringhot weather. Use clips or twist every otherrow in alternating cycles. This will preventthe climate from being affected due to re-duced transpiration by the handled plant.

Target Fruit Number

• Starting in May and through the summertarget 35 fruit/m2, or 25 fruit/m2 forcultivars that produce larger fruit. Excessivefruit loads will compromise plant growth.

• Target cumulative yield of 12 kg/m2 by mid-July. Selective fruit pruning to 20 – 30 fruit/m2 will improve fruit size.

• Harvesting 3 fruits/m2 per week encouragesbalanced growth. Exceeding 10 fruits/m2 perweek may result in a vegetative imbalance.

• Let primary and secondary flowers set on thethird set (5 to 6 fruit/stem) providing theplant is in balance.

• Target the fifth setting for the end of June inorder to target the sixth set for the end ofAugust for harvest in November.

• It takes an average of 8.5 weeks from set toharvest in the spring and fall and 7.5 weeksin the summer.

Target Fruit Grades/Size

• Extend the fruit development period bylowering ADT. This will produce larger,better quality fruit. Lowering ADT can beachieved by using roof sprinklers.

• Cull rates of 5% are common at this time ofyear. The majority of culls are associatedwith sunscald and knife cuts at harvest.

• Large fruit are more sensitive to sunscaldand cracking than medium and small-sizedfruit.

• BER is more frequent under high fruit loads.Do not remove fruit larger than 50 mmaffected by BER; it could upset fruit balanceof the plant.

• Harvest minimum once a week.


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Tab

le 4

-4. L

ate

spri

ng

an

d s

um

mer

pro

du

ctio

n c

ycle

/ M

ay-A

ug

ust

(w

eek

19 –

35)

G

row

ing

Str

ateg

y 1.

S

tart

: w

ith 2

5-35

frui

t/m2 a

nd a

pla

nt th

at is

slig

htly

veg

etat

ive

in b

alan

ce.

2.

Pro

mo

te:

plan

t bal

ance

by

mai

ntai

ning

spe

ed o

f gro

wth

, opt

imum

frui

t loa

d an

d st

agge

red

harv

est.

Mai

nten

ance

of b

alan

ce b

etw

een

grow

th

an

d fr

uit p

rodu

ctio

n w

ill m

axim

ize

over

all p

rodu

ctio

n.

3.

Fin

ish

: w

ith 2

5 fr

uit /

m2 b

y th

e en

d of

Aug

ust

Gro

wth

S

tag

e T

emp

erat

ure

(oC

) C

O2

(pp

m)

VP

D (

gra

ms/

m3 )

and

V

enti

lati

on

Ir

rig

atio

n

Pla

nt

Man

agem

ent

Vegetative growth

Set

AD

T b

etw

een

22o a

nd

23o , d

epen

ding

on

the

crop

st

reng

th

Set

min

imum

pip

e at

50o b

y 05

:00

and

drop

to 4

0o whe

n lig

ht is

hig

her

than

300

w

/m2 o

r 1

hour

afte

r su

nris

e

Dro

p th

e pi

pe to

20o

betw

een

19:0

0 an

d 23

:00

for

2-3

hr.

Use

a g

row

pip

e w

hen

light

in

tens

ity is

less

than

300

w

/m 2 to

pro

mot

e ai

r ci

rcul

atio

n

20-2

5 kg

/100

0m2 /h

r as

an

uppe

r en

d ta

rget

.

At 3

5 –4

0% o

pene

d ve

nts

use

700

- 80

0 pp

m w

hen

tem

pera

ture

is le

ss

than

25o C

and

de

crea

se to

350

–40

0 w

hen

tem

pera

ture

is

high

er th

an 2

5o C

Use

800

– 1

000

betw

een

late

af

tern

oon

to s

unse

t w

hen

vent

s ar

e 20

%

open

ed

Tar

get V

PD

3 -

7

If ou

tsid

e te

mpe

ratu

re

is le

ss th

an 8

o -se

t de

ad z

one

at 1

– 2

o an

d a

fast

act

ing

p-ba

nd

If ou

tsid

e te

mpe

ratu

re

is 1

2 o o

r hi

gher

–se

t de

ad z

one

at 0

.5o a

nd

slow

act

ing

p-ba

nd.

If ou

tsid

e te

mpe

ratu

re

is h

ighe

r th

an 2

5o –

set v

ent s

ettin

g de

pend

ent o

n lig

ht

Sta

rt ti

me

1.5

to 2

hrs

afte

r su

nris

e

Fin

ish

on s

unny

day

s at

sun

set;

on c

loud

y da

ys 2

-3 h

ours

bef

ore

suns

et

EC

feed

2.5

– 3

.0; p

H 5

.8 –

6.2

EC

dra

in 2

.8-3

.5; p

H 6

.5 –

6.8

Use

80

ml i

rrig

atio

n cy

cles

dur

ing

peak

ligh

t hou

rs a

nd r

educ

e nu

mbe

r bu

t inc

reas

e vo

lum

e to

10

0 –1

20 m

l afte

r

At 5

00-6

00 w

/m2 u

se 3

-4

irrig

atio

n cy

cles

/hr

At l

ight

inte

nsity

hig

her

than

700

w

/m2 u

se 5

-6 ir

rigat

ions

cyc

les/

hr

Add

1 n

ight

irrig

atio

n, if

req

uire

d

Tar

get O

D o

f 30%

whe

n fe

ed is

hi

gher

than

7L/

m2 /d

ay

Pru

ne to

2 le

aves

eve

ry 1

0 da

ys

Avo

id tw

istin

g an

d pr

unin

g du

ring

hot w

eath

er.

Do

not p

rune

abo

ve 1

0 cm

be

low

the

head

Let p

rimar

y an

d se

cond

ary

frui

t set

on

third

set

pr

ovid

ing

plan

t is

in b

alan

ce

Fruit set and

develop-ment

Set

day

tem

p 0.

5-1.

0o hi

gher

to e

nsur

e fa

ster

frui

t de

velo

pmen

t

Use

pre

-nig

ht to

enh

ance

se

tting

Use

700

to 1

000

to

prom

ote

frui

t set

ting

M

aint

ain

3 -

7VP

D.

Thi

s en

sure

s go

od

qual

ity f

low

ers.

Incr

ease

feed

EC

to 3

.5 a

nd

drai

n to

4.5

for

a sh

ort t

ime

to

enha

nce

frui

t set

.

Tar

get 3

5 fr

uit/m

2 for

a m

ediu

m fr

uit c

v. o

r 25

fr

uit/m

2 for

a la

rge

frui

t cv.

H

arve

st 3

frui

t/wee

k to

m

aint

ain

plan

t bal

ance

Bio

log

ical

Co

ntr

ol

Dis

ease

san

dP

hys

iolo

gic

alD

iso

rder

s C

ontin

ue m

onito

ring

to p

reve

nt o

utbr

eaks

of i

nsec

t and

mite

pes

ts.

Thr

ips:

A. c

ucum

eris

, O

rius

spp

. F

ungu

s gn

ats:

Hyp

oasp

is s

pp,

Aph

ids:

ban

ker

plan

ts w

ith A

phid

ius

spp.

Rel

ease

Aph

idol

etes

spp

. S

pide

r M

ites:

Use

P. p

ersi

mili

s fo

r co

ntro

l of o

utbr

eaks

Est

ablis

h pr

even

tive

cont

rol w

ith F

eltie

lla s

pp. S

teth

orus

spp

., an

d A

mbl

ysei

us s

pp.

Lo

oper

s: E

stab

lish

Pod

isus

spp

., T

richo

gram

ma

spp.

, Cor

tesi

a sp

p.

Mon

itor

for

the

pres

ence

of L

ygus

spp

. and

psy

llids

.

Wat

ch fo

r sy

mpt

oms

of d

isea

ses:

B

asal

ste

m d

isco

lour

atio

n -

Fus

ariu

m c

row

n ro

t. S

oft r

ot o

n fr

uit -

Rhi

zopu

s, E

rwin

i. P

hysi

olog

ical

frui

t dis

orde

rs:

soft

spot

s, s

ilver

ing,

BE

R ,s

unsc

ald,

mis

shap

en fr

uits

and

frui

t mot

tling

are

ofte

n as

soci

ated

with

sum

mer

hea

t str

ess.

R

oot c

ondi

tion

and

dise

ases

: C

heck

roo

t con

ditio

ns. F

lagg

ing

of th

e he

ad in

mid

-day

and

dis

colo

urat

ion

of r

oots

can

in

dica

te P

ythi

um in

fect

ion.


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per

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FALL PRODUCTION (September to November) Weeks 36 - 46

Light, Temperature and IrrigationAlthough close to the end of the growingseason, maintain growth speed and fruit devel-opment in order to establish the final fruit set.From September through November, accumu-lated light levels can range from 380-1450joules/cm2/day. During this period, light inten-sity and duration drops dramatically and there isa corresponding decline in temperature.

Reduced solar radiation combined with declin-ing fruit number/m2 and later the removal ofthe growing head, require careful reductions inthe irrigation cycles. This is to prevent fruitquality problems such as cuticle crackingcaused by excessive root pressure.

Reduced radiation combined with increasedoutdoor RH and low wind speed highlights theimportance of creating an active plant climateusing a combination of minimum pipe tempera-ture (45oC) and moderate venting.

In the fall the physical property of the media (airto water ratio) often declines due to composting.Maintain over-drain target in the fall and inspectthe growing media for general vigour of theroots. High RH, combined with full canopy andhigh water retention by the media translates intoless water demand by the plant. In the fall, longerperiods between irrigation cycles are preferred tokeep the roots active through the entire volumeof media. Frequent irrigation cycles cause rootsto deteriorate due to saturation of the mediawith water, breakdown of the physical structureof the media and oxygen deprivation.

Timing of the first and last irrigation must berelated to the water buffer available to the plantand depends on the condition of the media.Avoid irrigating before plants start to transpire.Irrigating too early in the day creates root pres-sure, causing fruit splitting and cuticle cracking.

Climate Strategies forVegetative Growth and FruitSet

Target temperatures• ADT, based on radiation, for August to

September is 20.5oC to 21.5oC; for October,20.0oC to 20.5oC; and for November, 19.0oCto 20.0oC.

• Maintain plant growth speed in order toachieve the last set by early to mid- Septem-ber. Note that new cultivars can set easily at20oC average temperature.

• ADT can be further dropped to 19oC -19.5oC only when the last fruit reachesmature green stage. This will delay ripeningof the fruit and may not ensure a betterprice.

• Increase temperature gradually, 1oC every 90–120 minutes, early in the morning when thelight levels reach 300 watts/m2. This willkeep tissue and air temperatures about equaland prevent condensation, reducing chancesof pathogen infections.

Pipe management• Maintain a minimum rail pipe of 50oC to

60oC two hours before sunrise to provide aircirculation at the base and throughout thecanopy to prevent Fusarium infections.

• The temperature near the rail pipe and nearthe heads can differ by more than 5oC. Thesedifferences can decrease the quality of fruit.To create an active climate, use the growpipe two hours before sunrise with setting of45oC at 0.5 metres below the head or 55oCat 1 metre below the head.

Ventilation• Set target temperature for venting to equal

target temperature for heating.


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• High RH outside and inside the greenhousecan lead to poor VPD (<3). Keep a mini-mum pipe (45oC) and slight vent to activatethe climate until light intensity is higher than300 watts/m2.

• A small vent of 3-5% may be required toremove moisture above the screen.

Screen Management• Open screens at sunrise, or one hour later if

outside temperature is still very cold.

• During the last three weeks of cropping, thescreen can be used more intensively. Keepthe screen closed when light intensity is lessthan 72 joules/cm2 /day but leave a smallopening. Open at light levels above 72joules/cm2 /day to improve humidity.

• Screens can be used to save energy whenoutside temperatures is lower than 12oC.Keep the screen closed and target a tempera-ture of 18 to 19oC. The heating set point forthe day can be lowered to 20oC.

Target C02

Maintain optimum levels of CO2 at 20 to 25

kg/1000 m2/hour for the establishment of thelast set. After the last set is established reducethis slightly to promote growth and speed.


EC

• Set EC of feed at 3.0. In the last 2-3 weeksreduce EC to allow roots to feed on residualsalts in the growing media.

• EC of the drain: September 2.5 to 3.0,October 3.0 to 3.5, November 3.5 to 4.0.The increase in EC reflects the decline in theirrigation volume.

pH

• Target feed pH between 5.8 and 6.2.

• Target drain pH between 6.5 and 6.8.

Over-drain

• In September apply approximately 3 L/m2/day with 40% over-drain in good light.

• In October and November gradually reducevolume of irrigation to 1.5 L/m2/day with20% over-drain.

Irrigation

• During sunny weather the plants still requirehigh amounts of water at mid-day. Reducethe frequency and increase the volume ofirrigation cycles. Higher volume (150-200ml)will prevent saturation and maintain evenmoisture and optimum EC in the media.

• Start watering two hours after sunrise andstop two hours before sunset. Watering tooearly can create silvering and cuticle crackingin fruit due to high root pressure. In darkweather, start watering 3 to 4 hours aftersunrise to maintain fruit quality.

• Keep a slightly drier slab by increasing theirrigation volume from 120 to 150mL/cycle.This will promote more oxygen in the grow-ing media.

Nutrients

• Target drain K:Ca:Mg ratio at 6.0 : 4.0 : 3.0-3.5 millimoles, respectively.

• At EC below 3.0, increase micronutrients by25% in both A and B tanks.

Plant Management

Target Leaf Number• Prune to one leaf providing the plant is not

too generative. Plants require less coolingand shading in September when the radiationintensity and duration are reduced.

Topping and Pruning• Topping is recommended only after the last

fruit set. Remove the head in mid- to lateSeptember to aid in fruit sizing


4.

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• Maintain regular pruning and remove longershoots back to the main stem.

• For late setting, which can take place in thebeginning of October, keep the side shootsshort so the flowers can get maximum light.To aid setting during the last set do notprune or train the crop during this time andtemporarily reduce irrigation by starting laterand stopping earlier.

• Maintain 20-35 fruit/m2 ; 25 fruit/m2 forlarge-fruited cultivars.

• Remove any poor quality fruit.

• Target fruit grade-out of 7% XXL (minimumdiameter of 90mm); 42 to 57% XL (mini-mum diameter of 80mm).

Conditions Influencing Late SettingIn order to optimize the last set and obtainmature fruit by November, plants are usuallytopped by mid-September. Occasionally, top-ping is left to early October and harvest isextended into December. Plant balance is animportant factor influencing the last setting. Inorder to maintain plant balance, target thecorrect number of fruit per plant and optimizeRH, irrigation supply and stem density. It isalso important to use pre-night temperatures toinitiate this last flower set.

Fruit per PlantFlower quality declines with decreasing lightintensity and the number of newly initiated fruitwill be less than the number being harvested.This results in a declining number of fruit perplant. The reduction of fruit load should nothappen too fast or be too dramatic. Avoid heavyfruit thinning as it can cause a surge in vegeta-tive growth and lead to poor quality flowers thatare hidden in the plant head.

Root TemperatureIn the fall a lower or reduced root temperaturehas a positive effect on fruit set. Avoid highpipe temperatures (50 to 60°C) during late fruitsetting. Use low irrigation temperatures (12 to14oC) to improve oxygen availability for roots.This also provides a generative signal to theplant and aids the last fruit set.

Stem DensityThe three-stem system is beneficial in the springbut under fall conditions, it creates too muchcompetition among the stems. This results inweaker flowers than in the two-stem system.


4.

Pep

per

Pro

du

cti

on

Tab

le 4

-5.

Fal

l pro

du

ctio

n c

ycle

/ S

epte

mb

er-N

ove

mb

er (

wee

k 36

– 4

6)

Gro

win

g S

trat

egy

1.

Mai

nta

in p

lan

t sp

eed

an

d f

ruit

har

vest

in o

rder

to

ach

ieve

th

e la

st s

et b

y ea

rly

to m

id-S

epte

mb

er.

2.

Cre

ate

an a

ctiv

e cl

imat

e w

ith

min

imu

m p

ipe

tem

per

atu

re o

f 40

if li

gh

t <

810

jou

les/

cm2 a

nd

mo

der

ate

ven

tin

g.

3.

Tar

get

a h

ealt

hy

roo

t sy

stem

by

care

ful c

on

tro

l of

wat

er a

nd

oxy

gen

leve

ls in

th

e sl

ab

Gro

wth

S

tag

e T

emp

erat

ure

(oC

) C

O2

(pp

m)

VP

D (

gra

ms/

m3 )

and

V

enti

lati

on

Ir

rig

atio

n

Pla

nt

Man

agem

ent

Vegetative growth

Set

AD

T b

etw

een

20o a

nd

20.5

o in S

ept.

& O

ct.;

and

19o to

20o in

Nov

. bas

ed o

n ra

diat

ion

leve

ls

Ful

l can

opy

requ

ires

min

imum

pip

es 4

0o if th

e lig

ht le

vels

are

less

than

81

0 jo

ules

/cm

2

Dur

ing

clea

r co

ld n

ight

s pr

even

t hea

ds fr

om

reac

hing

low

tem

pera

ture

s,

part

icul

arly

in lo

w

gree

nhou

ses

20-2

5 kg

/m2 /h

r es

peci

ally

to a

id th

e la

st s

et.

Tar

get V

PD

4 –

7 tw

o ho

urs

befo

re s

unris

e

45o to

60o p

ipe

until

tw

o ho

urs

afte

r su

nris

e or

>67

5 jo

ules

/cm

2

Avo

id la

rge

vent

op

enin

g w

hen

outs

ide

tem

p.<1

5o C w

ith lo

w

radi

atio

n

Sta

rt ti

me

2 to

3 h

rs a

fter

sunr

ise

Fin

ish

2-3

hour

s be

fore

sun

set

EC

feed

3.5

; pH

6.0

EC

dra

in 2

.5-4

.0; p

H 5

.8 –

6.8

Firs

t irr

igat

ion

may

be

dela

yed

to 3

-4 h

rs a

fter

sunr

ise

in d

ark

wea

ther

to p

reve

nt fr

uit q

ualit

y pr

oble

ms

Res

tric

t irr

igat

ion

feed

rat

e to

al

low

a d

rier

slab

and

pro

mot

e m

ore

oxyg

en. T

his

can

be d

one

by in

crea

sing

cyc

le v

olum

e fr

om 1

20 to

150

ml

Rem

ove

head

in m

id-

to la

te

Sep

t to

aid

frui

t siz

ing

A “

soft

pinc

h” to

all

extr

a fo

liage

to p

rote

ct th

e fin

al

pepp

er s

et fr

om th

e su

n

35 to

40

frui

ts/m

2 , rem

ove

poor

qua

lity

frui

t

Eth

rel o

ptio

n fo

r re

mai

ning

fr

uit

Fruit set a

development

nd

Set

day

tem

p 0.

5-1.

0 o C

hi

gher

to e

nsur

e fa

ster

frui

t de

velo

pmen

t

Use

pre

-nig

ht to

enh

ance

se

tting

Use

700

to 1

000

ppm

to

pro

mot

e fr

uit

setti

ng

Mai

ntai

n 3

– 7

VP

D.

Thi

s en

sure

s go

od

qual

ity fl

ower

s.

Incr

ease

feed

EC

3.5

and

dra

in

to 4

.5 fo

r a

shor

t tim

e to

en

hanc

e fr

uit s

et.

Tar

get 3

5 fr

uit/m

2 for

a m

ediu

m fr

uit c

v or

25

frui

t/m2 fo

r a

larg

e fr

uit c

v.

Har

vest

3 fr

uit/w

eek

to

mai

ntai

n pl

ant b

alan

ce

Bio

log

ical

Co

ntr

ol

Dis

ease

san

dP

hys

iolo

gic

alD

iso

rder

sC

ontin

ue m

onito

ring

to p

reve

nt o

utbr

eaks

of i

nsec

t and

mite

pes

ts.

Aph

ids:

use

Aph

idiu

s sp

p. o

r A

phid

olet

es d

epen

ding

on

the

pres

ence

of

hype

rpar

asiti

sm. M

onito

r po

pula

tions

of n

atur

ally

occ

urrin

g pr

edat

ors

in

the

gree

nhou

se.

Spi

der

Mite

s: U

se P

. per

sim

ilis

for

cont

rol o

f out

brea

ks.

Mon

itor

for

the

pres

ence

of L

ygus

spe

cies

and

psy

llids

.

Wat

ch fo

r sy

mpt

oms

of d

isea

ses:

B

asal

ste

m d

isco

lora

tion

- F

usar

ium

cro

wn

rot.

Sof

t rot

on

frui

t - R

hizo

pus,

Erw

inia

. P

hysi

olog

ical

frui

t dis

orde

rs:

soft

spot

s, s

ilver

ing,

BE

R ,s

unsc

ald,

mis

shap

en fr

uits

and

frui

t mot

tling

are

ofte

n as

soci

ated

with

late

sum

mer

hea

t str

ess.

R

oot c

ondi

tion

and

dise

ases

: W

atch

for

sign

s of

flag

ging

of t

he h

ead

in m

id-d

ay; t

his

may

indi

cate

a P

ythi

um

infe

ctio

n. R

oots

infe

cted

with

Pyt

hium

hav

e br

own

soft

tissu

e as

opp

osed

to

whi

te fi

rm r

oots

.


4.

Pep

per

Pro

du

cti

on


5.

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t 5. PEST AND DISEASE MANAGEMENT

The management of insect and mite pests is anessential part of crop production and its mainobjective is to maintain pest populations levelsbelow the damage threshold. Effective pestmanagement requires implementation of inte-grated pest management programs during thegrowing season and thorough end-of-year cleanup.

Integrated Pest

Management (IPM) for

Insect and Mite PestsIPM uses cultural, biological, and chemicalcontrols together with pest monitoring toprevent or suppress outbreaks of insect andmite pests. Pesticides are part of IPM but theyare used only when monitoring indicates thatbiological and cultural controls have not beeneffective. IPM has gained industry-wide ac-ceptance whereas sole reliance on chemicals inthe past has lead to the development of resist-ance and the buildup of secondary pests. Keycomponents of effective IPM programs include:crop monitoring, cultural control, biologicalcontrol, and chemical control.

Monitoring

Monitoring is key to a successful IPM program.An effective monitoring program should in-clude the following components:

Trained staff to recognize the feeding damageand pest species. Every greenhouse shouldhave a pest manager to oversee the IPM pro-gram, but the crop workers should also beactively involved in crop monitoring. Timeinvested in training crop workers to recognizeand flag damaged infestation areas will result inmore effective pest control and less crop dam-

age. The presence of unusual symptoms orpests should be reported immediately to atrained entomologist.

Regular crop monitoring is necessary for detec-tion of pests before economic damage canoccur. The effectiveness of biological controlsis greatly improved when implemented againstlow number of pests.

Maintaining good monitoring records is funda-mental for effective IPM. Record the location,size and intensity of an infestation and changesin pest populations from week to week. Alsorecord the release and establishment ofbiocontrol agents and assess the progress ofbiocontrol programs.

Note: There are several commercial IPMmonitoring services available to provide weeklymonitoring and control recommendations.

Monitoring procedures include visual inspec-tion of the crop, and use of coloured stickytraps and pheromone traps. The method ofmonitoring is determined by the pest species.For example, two-spotted spider mites andaphids are monitored by visual inspection ofthe plant canopy. This can be done in conjunc-tion with crop pruning and tying operations.

Yellow sticky traps can be used to detect thepresence and number of thrips, greenhousewhiteflies, aphids, and fungus gnats. They willattract some bio-control agents, i.e. Aphidius

species. Blue sticky traps are very effective formonitoring thrips and aphids, but do not attractother pests. Thrips and whiteflies are usually foundin the traps before they are detected on the plantsand long before they can cause any damage.


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Choice of size and design of sticky traps isinfluenced by their cost and ease of handling.Position the traps just above the heads until theplants reach the wire and then hang them fromthe wire. Traps should be changed at leastevery 2 to 4 weeks and more often in hotweather as the glue dries more quickly. Use atleast one trap per 100 pepper plants to detectthrips. They should be distributed evenlythroughout the greenhouse, with extra trapslocated in areas that tend to harbour pests:doorways, vents and the ends of rows. It iscritical that the traps are checked at least oncea week to detect increases in pest populationspromptly.

Pheromone traps release a synthetic sex attract-ant luring male adult moths. Trap catchesindicate that the adults are active (flying), thefemales are laying eggs, and it is time to startcontrol actions. Although traps can help detectpests and hence the timing of control actions,they do not reliably indicate the number ofpests and are not useful for determining treat-ment thresholds. Check traps at least once aweek and record the number and species ofmoths trapped.

Crop monitoring should begin during propaga-tion. Indicate preference for the control meth-ods (chemical or biological) to the propagatorand request a history of pests encounteredduring propagation. If there is a need to applypesticides, make sure they are compatible withyour biocontrol programs and do not have longresidual times. Monitoring frequency should beincreased as the ADT increases.

Cultural Control

Cultural control is one of the main methods ofpreventing outbreaks or spread of some green-house pests. For example, well-managed draincollection and good sanitation of the green-house will keep the populations of fungusgnats, shore flies and moth flies below theeconomic threshold.

Once an area is infested with spider mites,foxglove aphids or potato aphids, good cultural

practices can minimize the pests spreadingwithin the greenhouse. This can be done byplacing infested prunings in closed containersand by scheduling work in an infested area atthe very end of the day, to minimize the spreadof pests that may land on workers’ clothing,carts and equipment.

Good crop maintenance is another importantcomponent of cultural control. The plantsmust be regularly pruned and twined; all cropdebris should be promptly removed from thegreenhouse and its vicinity. Remove any weedsthat happen to gain a foothold through gaps inthe floor plastic and repair the floor. Personalplants such as houseplants should not be al-lowed in the greenhouse. Both weeds andhouseplants can be a source and refuge forpests and diseases.

Weeds growing around the greenhouse can hostmany insect pests. Maintain a well-managedbuffer zone around the greenhouse by regularlymowing the grass and weeds.

Biological Control

Biological control is defined as the use ofbiocontrol agents, primarily predators andparasites, to control insect and mite pests. Itsobjective is to maintain pest population levelsbelow the damage threshold. Biological controloften results in suppression but not eradicationof the pest populations; some surviving pestsare required to maintain the reproductive cycleof many predators or parasitoids.

Biological control is most effective when intro-duced at the first occurrence of pests because itallows ample time for the establishment ofbiocontrol agents and prevention of serious pestoutbreaks. Preventive control relies on theintroduction of biocontrol agents throughout theinfested area or the entire greenhouse. Subse-quent releases should be made mainly in pestoutbreak locations. Introductions into heavyinfestations have little chance for successfulcontrol. Specific pest control strategies are givenin the following sections.


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The increased use of biological controlsthroughout the greenhouse industry has led to asignificant reduction in pesticide applications.The B.C. greenhouse vegetable industry hasbecome a world leader in environmentallysustainable, intensive crop production.

Quality Control forCommercially AvailableBiologicalsMost biologicals should be kept at 10 to 15°Cduring shipping and storage. Warmer or coolertemperatures may have an adverse effect onsurvival and performance. For example, preda-tors shipped at higher than optimal temperaturecould starve or have an extended non-reproduc-tive period after release in the greenhouse. Checkthe condition of the package on arrival and makesure the temperature of the package contents iswithin required range. Contact the supplier if thepackage is excessively warm or cold.

Check the shipping and arrival dates for ship-ping delays and keep the shipment records andbatch number. Record when and where theywere released in the greenhouse.

Encarsia formosa

On arrival, use a hand lens to inspect the cardsfor the presence of emerged or dead parasitoidsor scales with emergence holes. A shipment ofE. formosa should have only an occasional deadparasitoid or exit hole.

Select one or two cards from the shipment andmake a quick count of the black scales. Puteach card in a separate plastic bag or twist-onPetri dish. Keep them in a warm but shadyplace and inspect for emergence over a two-week period. Count the number of emergedadults and compare the result with label specifi-cations from the supplier.

Aphidius spp. andAphelinus abdominalis

These aphid parasites are shipped either asadults or as pupae in mummified aphids. Whenshipped as adults, check the lid and walls ofthe container for actively moving insects.When shipped as pupae, select several mum-mies and allow them to emerge. Follow asimilar procedure as for E. formosa.

Aphidoletes aphidimyza

This predator is shipped as pupae in an inertmedium such as damp vermiculite. Keep aportion of the shipment in the shipping con-tainer with the lid closed and let the insectsemerge. Release the rest in the greenhouse.Keep in mind that you have to check thecontainer every day to release the emergedadults, or you will have wasted them.

Phytoseiulus persimilis,Amblyseius cucumeris andHypoaspis spp.

These predatory mites are shipped in an inertmedia. You should be able to see the predatorson the lid and walls of the container when youopen the package. If there is no obviousactivity, mix the medium well by rotating thecontainer gently and pour some onto a sheet ofwhite paper. Predators should be visible andmoving about. P. persimilis shipped on leavesshould be active.

Orius insidiosus

This predatory bug is shipped as an adult. Theyshould be visible immediately through the lidof the container. After releasing them, checkthe bottom of the containers for dead bugs.

Check with distributors of biological controlagents for additional recommendations anddemonstrations of an assessment of quality ofshipped product. To sustain the good qualityof the natural enemies follow the label recom-mendations included with the shipment regard-ing storage, handling, and releasing. Never


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leave them in the sun or store them at less than10°C. In general, predators and parasitoidsshould be released during the coolest part ofthe day so that they become active and emergeas the day becomes warmer.

Recently, new standards have been developedthrough the American Society for Testing andMaterial International (ASTM) for the quantifi-cation of P. persimilis and E. formosa, but it is atime-consuming process to assess the quantitiesaccurately. New quick and user-friendly meth-ods are being developed.

Chemical ControlPesticides are an essential part of IPM pro-grams. They are used when biological andcultural controls are not available or have notbeen effective. Chemical control can be usedalong with biological control programs tosuppress localized pest outbreaks, e.g. spottreatments of heavily infested areas.

Although effective in controlling target pests,application of pesticides can have a variety ofside effects. Pesticides can cause a varyingdegree of mortality of biological agents, whichcan lead to outbreaks of secondary pests.Contact with pesticides can irritate manyinsects, leading to the dispersal of either pestsor beneficials throughout a greenhouse. Thepersistence of a pesticide residue can affect theestablishment of biocontrol agents. Applica-tions of some pesticides can cause plant stressor phytotoxicity that reduces the productivityof the pepper plant and increases its suscepti-bility to other pests and diseases. Finally, themisapplication of pesticides can create environ-mental and food safety problems. The choiceof chemical control should always consider thehazard to the plant and biocontrol programs.

See page 147 for a list of pesticides used inpepper greenhouses in B.C. Information oncompatibility of pesticides with biocontrolagents is available from your supplier and at thefollowing websites:

http://www.biobest.be/(look under side effects)

http://www.koppert.nl/e005.shtml(look under side effects)

Greenhouse Cleanup andOther Factors AffectingInsect & Mite SurvivalAs fall approaches lower light intensities, shorterdays and the corresponding change in temperatureand relative humidity result in the progressivedecline in the quality of the greenhouse crop.Changing climate conditions, particularly daylength and temperature, and the quality of thepepper plant are key factors influencing insect andmite pest physiology and behaviour. Greenhouseweeds, crop debris and cleanup disturbances canalso affect pest survival. See also GreenhouseCleanup, page 129.

Day Length

Shorter days signal approaching winter condi-tions. Some pest species respond by enteringdiapause, i.e. a quiescent period of greatlyslowed physiological processes. The two-spotted spider mite starts diapausing in latesummer and early fall. Some aphid speciesrespond by dispersing to over-wintering hosts.Others take short-range flights to fresh hostsand preferred weed species outside of thegreenhouse. Some pests are unaffected by theday length, e.g. cabbage looper.

Temperature

Insects are ‘cold-blooded’ and their movementand physiological processes are slow at lowtemperatures and fast at high temperatures,which is why pest managers use the concept of‘degree-days’ (DD) to measure insect develop-ment. Insects will reach the same developmen-tal stage when kept for 10 days at 20 °C or 20days at 10°C. The low temperatures duringcrop removal and cleanup slow the insects’physiology allowing them to survive a relativelylong time, often until the introduction of the


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new crop. Under cold conditions insect repro-duction is delayed, flight is impossible and theyhave a tendency to hide in over-winteringquarters. Pesticides are less effective wheninsect physiology is slowed. Pest control atreduced temperatures is almost impossible.This emphasizes the importance of effectivepest control in the late summer and early fall.

In the fall the glass surface can be very cold andcabbage loopers, potato psyllids and green-house whiteflies that land on the glass cansurvive for long periods.

Host Quality

Declining plant quality can increase the pest’stendency to diapause or dispersal. In particular,larger numbers of spider mites will diapauseearly in the fall if plant quality is low.

Weeds

During cleanup, weeds are important alternatehosts for aphids, whiteflies, thrips, spider mites,psyllids and caterpillars. In the cold pests cansurvive a surprisingly long time on even themost inhospitable plants. Weeds inside andoutside the greenhouse, particularly cress andOxalis species, are potential over-winteringsites and short-term refuges. Greenhousewhiteflies can over-winter outside on manyevergreen plants. Lygus species also requireaccess to fresh plant material throughout thewinter as they periodically feed during hiberna-tion. Aphids that over-winter as adults cancontinue to reproduce on many weed speciesinside and outside the greenhouse.

Debris

Plant debris can provide a short-term refuge forinsect pests. Greenhouse whiteflies and aphidscan complete development on leaf debris as itdries on the floor. Debris can protect spidermites, whiteflies, aphids and thrips from expo-sure to fumigants and other cleanup chemicals.

The number of pests carried over from season’send determines how soon pest outbreaks willoccur in the new crop, i.e. the more pests that

are carried over the sooner they will break out.Careful attention to cleanup is of utmostimportance. Economic constraints such as gasprices or pepper prices can affect how cleanupis conducted. If gas prices are high the green-house temperature might be kept very lowduring the inter-crop period, increasing poten-tial carryover of many insects. If product pricesare high the inter-crop period might be elimi-nated to maximize the production time.

Stages in Cleanup

End-of-seasonThe crop has completed flowering, the lastfruits are ripening and the plant is beginning tosenesce. Daylight decreases from 12 to 8 hoursand light intensity decreases. The major con-cern at this time is to protect the plants fromserious pest outbreaks, to minimize pestsentering diapause and to reduce populations ofpests to be dealt with at crop removal.

High populations of spider mites during Augustto early September will trigger many of them todiapause and hide in the greenhouse structurewhere they cannot be reached by cleanup opera-tions. They may emerge in late winter or spring,causing outbreaks and severe plant damage.

Emphasize biological control in September toreduce pest numbers, with continued monitor-ing in October to help plan pest control re-quirements during cleanup. Switch to chemicalcontrol before removing the plants. Removeweeds inside and outside the greenhouse toreduce pest refuges.

End-of-cropBefore physical removal of the crop, the irriga-tion system is turned off to dry down the mediaand reduce the plant weight. During this time,physical disturbances are frequent and tempera-ture is often reduced to reduce heating costs.Fumigate the greenhouse as soon as the plantsare removed from the greenhouse. Presence ofthe new crop in the greenhouse during cropremoval poses an extreme risk of pest transferand infestation.


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Inter-cropThe greenhouse is empty and temperature islow. The greenhouse structure and mechanicalsystems are power washed and sterilized,rooting media are replaced and the plastic maybe replaced.

The new crop should not be brought into thegreenhouse until the old crop has been com-pletely removed and the cleanup process iscomplete. Although usually not economicallyfeasible, high greenhouse temperatures increasethe insects’ need for water and food causingmany to die.

Remove plant debris and weeds from thegreenhouse and the surrounding property.Greenhouse whiteflies can fly during the winterand on a warm winter day could fly from adebris pile, through a vent and back into thegreenhouse. Inspect the walls for trapped pests,and the fixtures, posts and curtains fordiapausing spider mites and pupating loopers.Pressure wash the structure, apply dormant oilto the concrete and around posts, and removeplastics and other disposable materials beforebringing in the new plants.

New CropIntroduction of the new crop is a short andoften-overlooked period when you will eitherbenefit from a thorough cleanup or pay theprice for a poorly executed job. Consider moni-toring and applying biological controls duringpropagation. The knowledge acquired will helpin planning the new crop pest managementprograms. Some biological controls are affectedby day length and are not suitable for use fromDecember to March. Avoid systemic insecti-cides as they can have long residual times andaffect the establishment of natural enemies.The new growth is soft and susceptible todamage. Begin monitoring as soon as the cropis planted by trapping and by visual inspectionfor initial pest invasions. Spot spray withproducts that are compatible with bio-controlagents when necessary to reduce the size andspread of infestations.

A careful and thorough cleanup is arguably themost important step in reducing pest problemsin the new growing season. Day length, tem-perature, crop quality, alternate hosts andheating costs affect the cleanup process. Effec-tive pest management at cleanup will paydividends in reduced IPM costs, reduced lossesand ultimately high yields in the new growingseason.

The Major Insect andMite Pests

Aphids

Taxonomy and AppearanceThe four species of aphids commonly found ongreenhouse peppers in BC are:

• green peach aphid, Myzus persicae;

• cotton/melon aphid, Aphis gossypii;

• potato aphid, Macrosiphum euphorbiae;

• foxglove aphid, Aulacorthum solani.

Other aphid species as well as off-type clonesmay be found occasionally on greenhousepeppers. An example is the violet aphid, Myzus

ornatus. This species is mostly solitary, and hasnot yet caused problems. See Figure 5-1 forphysical descriptions of the four main species.

Generalized Aphid Life CycleAphids have a complex life cycle, but on green-house peppers they develop mainly asunfertilized, wingless females. Winged formsdevelop occasionally in response to (1) seasonalchanges in climate, (2) overcrowding, or (3)poor condition of the host plants. The wingedforms tend to disperse and start new coloniesthroughout the greenhouse.

Aphids have a very high reproductive capacity.At 20 oC each wingless adult can produce 40 to100 female offspring that in turn mature andstart to reproduce in less than 10 days. Theirhigh reproductive capacity allows aphids toincrease to damaging levels in a very short time.


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Feeding DamageAphids have piercing and sucking mouth-partswith which they feed on the plant sap. Duringfeeding they inject saliva into the plant tissue.Aphid feeding negatively affects pepper yield inseveral ways.

Stunted growth and deformation: Feeding byhigh numbers of aphids may cause distortedleaves and stems and stunted plant growth. Thesaliva of some species may cause the leaftissue to discolour or deform. This can beevident even at low infestation levels.

Honeydew secretions: All aphid speciessecrete honeydew. Large deposits of honeydewpromote development of sooty mould on thefoliage and fruit. The sooty mould can reducethe yield by reducing photosynthesis. Honey-dew and sooty mould reduce the marketabilityof fruit. See colour photo 15.

Viruses: Aphids can transmit over 100 viruses,many of them are of concern to pepper grow-ers. Examples include: tobacco mottle virus,pepper mottle virus, tobacco ringspot virus,and tobacco wilt virus.

Figure 5-1. Identification of the four aphid species found commonly on greenhouse peppers

green peach aphid

melon aphid potato aphid foxglove aphid ad

ult

s

size

an

d c

olo

ur

of

win

gle

ss a

du

lts

small to medium (1.2 - 2.2 mm)

pale green; sometimes can be pink or red. See colour photo 11.

small to medium (0.9 – 1.8 mm) light green mottled with dark green; sometimes can be brown and yellow. See colour photo 13.

medium to large (1.7 –3.6 mm) with a pear-like or spindle body shape a shade of light green, sometimes can be yellow or pink. Eyes are distinctly reddish. See colour photo 12.

medium to large (1.8 – 3.0 mm) transparent light green to green. The tips of the antennae, cornicles, legs and the leg joints are dark. Head has a faint rust-brown color. See colour photo 14.

hea

d

tubercles are large and

lean towards each other

tubercles are absent and forehead is relatively flat

tubercles are large and angle away from each

other

tubercles are large and parallel

abd

om

en

cornicles are green and slightly swollen toward the tips

cornicles are black, short and stout

cornicles are long and about 1/6th of the distal end is black.

cornicles have a dark green spot at the base, and no swelling on the distal half

Figure 5-1. Identification of the four aphid species found commonly on greenhouse peppers


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Preventive StrategiesPreventive strategies for aphid control rely onrepeated releases of parasitic wasps or predatorymidges or the employment of a ‘banker plant’system to provide alternate hosts to serve as areservoir of the natural enemies.

Banker plant system

Banker plants are potted grasses, usually wheat,oats or barley, which have been inoculated withgrass-feeding aphids and subsequently with aparasitic wasp. The banker plants provide asteady supply of parasitoids. This ensures thataphids are attacked by parasitoids before theirnumbers can increase to damaging levels.

Preventive control of green peach and melonaphids relies on introduction of banker plantsinoculated with Aphidius matricariae or A. colemani,

whereas control of foxglove and potato aphidsuses banker plants inoculated with Aphelinus

abdominalis.

The first banker plants should be introduced assoon as the new crop is planted. Fresh bankerplants should be added every 8-12 weeks. Thepots are suspended above the crop canopy at aminimum density of 10 pots/hectare. They areoften positioned along the walkway. Growerexperience, however, suggests that control ofaphids is improved when the density of bankerplants is higher than 10 pots/ha and when thepots are distributed among the plants rather thanalong the pathways. See colour photo 16.

Effectiveness of the parasitoids and banker plantsystem decreases in the presence ofhyperparasitoids. These are naturally-occuringwasps that parasitize developing A. colemani,Aphidius ervi or A. abdominalis inside an aphidmummy. Emerging from the mummy thehyperparasitoid produces an exit hole with a jaggededge. The exit hole of the beneficial wasp is roundwith an even edge (see Figure 5-2).Hyperparasitoid populations increase in the sum-mer although they are occasionally observed in thespring. Start monitoring for the presence ofhyperparasitoids in the spring and monitor bothcrop and banker plants. As soon as they are de-tected, change the preventive control of aphids torepeated releases of the predatory fly, Aphidoletes.

Differences in Biology and Behaviourof the Four Aphid Species and Impli-cations for Control

The extent of damage caused by the four aphidspecies depends on a number of circumstances.All these factors need to be considered whendeveloping control strategies to prevent orminimize damage:

• plant age;

• infestation levels – low, medium or high;

• location of feeding – top, middle or lowercanopy;

• type of feeding damage – growth distortionand/or honeydew secretion;

• dispersal behaviour and colony structures.

Plant AgeYoung pepper plants are more susceptible tofeeding damage than mature plants. The damageinflicted during the first and second fruit set hasmore economic impact than damage inflicted laterin the season. Pepper fruit has the highest retailvalue during the early spring and the loss of thefirst and/or second fruit set can reduce or eliminatethe profit margin. Plants stunted by aphid feedingat early growth stage often remain shorter and lessvigorous for the rest of the season. As a resulttolerance for aphid damage in January and Februaryis very low. This is why timely establishment ofpreventive controls and well-executed curativetreatment of early aphid infestations are of criticalimportance (see Tables 5-1 and 5-2). For a sum-mary of the commercially available biocontrolagents used in aphid control, see Table 5-3.

Figure 5-2.

(A) A round, even-edged exit hole is created by a

parasitoid and (B) jagged-edged exit hole

is created by a hyperparasitoid.

A B


5.

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Tab

le 5

-1.

Su

mm

ary

of

IPM

str

ateg

ies

for

the

gre

en p

each

ap

hid

.

Sea

son

M

on

ito

rin

g

Co

ntr

ol S

trat

egie

s

Winter (December -

February)

Mon

itor

mid

dle

and

top

of th

e ca

nopy

for

the

pres

ence

of a

phid

s or

cas

t ski

ns.

Wat

ch fo

r de

form

ed h

eads

, dow

nwar

d cu

pped

le

aves

and

hon

eyde

w s

ecre

tions

.

Pre

vent

ive

cont

rol o

f the

gre

en p

each

aph

id r

elie

s on

intr

oduc

tion

of b

anke

r pl

ants

with

A.

mat

ricar

iae

or A

. col

eman

i or

repe

ated

rel

ease

s of

thes

e pa

rasi

toid

s.

To

cont

rol a

n ap

hid

outb

reak

, use

rep

eate

d ap

plic

atio

ns o

f Aph

idiu

s sp

p. R

elea

se

Aph

idol

etes

and

lady

beet

les

if th

e ap

hid

prob

lem

is w

ides

prea

d. T

he tw

o pr

edat

ors

will

re

duce

the

popu

latio

n to

a m

anag

eabl

e le

vel,

but A

phid

olet

es o

ffspr

ing

will

not

rep

rodu

ce a

t th

is ti

me

of th

e ye

ar u

nles

s su

pple

men

tary

ligh

t is

used

. If

aphi

d nu

mbe

rs b

ecom

e un

man

agea

ble

cons

ider

app

licat

ion

of n

icot

ine

fum

igan

t.

Spring (March – April)

Mon

itor

as d

urin

g th

e w

inte

r. A

sses

s th

e es

tabl

ishm

ent a

nd a

bund

ance

of A

phid

ius

spp.

and

Aph

idol

etes

and

adj

ust y

our

rele

ases

ac

cord

ingl

y. L

ook

for

sign

s of

hy

perp

aras

itism

: ja

gged

-edg

ed e

mer

genc

e ho

les

in th

e ap

hid

mum

mie

s. M

onito

r th

e pe

pper

flow

ers

for

the

pres

ence

of w

inge

d ap

hids

. Inf

lux

of w

inge

d ap

hids

sig

nals

an

incr

ease

of a

phid

pop

ulat

ions

.

Mai

nten

ance

of l

ow in

fest

atio

ns d

epen

ds o

n co

ntin

uous

sup

ply

of A

phid

ius

spp.

thro

ugh

repe

ated

rel

ease

s or

ste

ady

mai

nten

ance

of t

he b

anke

r pl

ant s

yste

m.

Incr

ease

the

rele

ase

rate

s if

win

ged

aphi

ds a

re o

bser

ved

in th

e flo

wer

s.

Intr

oduc

e pa

rasi

tic w

asps

and

pre

dato

rs to

con

trol

gre

en p

each

out

brea

ks. C

urat

ive

appl

icat

ions

of A

phid

olet

es a

nd la

dybe

etle

s ar

e th

e fir

st li

ne o

f con

trol

. The

y w

ill r

educ

e th

e ap

hid

popu

latio

n in

a s

hort

per

iod

of ti

me

to a

man

agea

ble

leve

l. R

elea

se A

phid

ius

spp.

at

the

sam

e tim

e an

d co

ntin

ue r

elea

ses

for

2-3

wee

ks. T

he im

pact

on

the

aphi

d po

pula

tion

will

no

t be

appa

rent

unt

il 3

or m

ore

wee

ks a

fter

the

initi

al r

elea

se. O

nce

esta

blis

hed,

they

will

pr

ovid

e ef

fect

ive

and

long

-last

ing

cont

rol.

Summer (May – August)

Mon

itor

the

low

er c

anop

y fo

r w

ingl

ess

aphi

ds

and

pepp

er fl

ower

s fo

r w

inge

d ap

hids

. Inf

lux

of w

inge

d ap

hids

sig

nals

incr

ease

of a

phid

po

pula

tions

. Ass

ess

para

sitis

m le

vels

, and

lo

ok fo

r hy

perp

aras

itism

. Tim

ely

dete

ctio

n of

hy

perp

aras

itism

and

win

ged

adul

ts a

nd th

e co

rres

pond

ing

adju

stm

ent o

f con

trol

str

ateg

ies

are

criti

cal t

o su

cces

sful

bio

logi

cal c

ontr

ol

durin

g la

te s

umm

er a

nd fa

ll.

At l

ow in

fest

atio

n, fe

edin

g of

gre

en p

each

aph

ids

has

no e

cono

mic

impa

ct o

n pe

pper

pr

oduc

tion

beca

use

they

feed

mos

tly b

elow

the

harv

este

d fr

uit a

nd d

o no

t dep

osit

hone

ydew

on

the

frui

t. T

his

shou

ld n

ot b

e in

terp

rete

d as

an

indi

catio

n to

eas

e of

f pre

vent

ive

cont

rol.

Mai

nten

ance

of p

reve

ntiv

e co

ntro

l is

very

impo

rtan

t at t

his

time

to a

void

aph

id o

utbr

eaks

; co

ntin

ue w

eekl

y re

leas

es o

f Aph

idiu

s sp

p. I

n th

e pr

esen

ce o

f hyp

erpa

rasi

toid

s, in

ocul

ate

bank

er p

lant

s w

ith A

phid

olet

es o

r re

peat

rel

ease

s of

this

pre

dato

r. E

xact

rel

ease

rat

es

depe

nd o

n th

e po

pula

tion

leve

ls o

f the

aph

id, A

. col

eman

i, A

phid

olet

es, a

nd la

dybe

etle

s as

w

ell a

s na

tura

lly o

ccur

ring

syrp

hid

flies

and

lace

win

gs. I

f win

ged

aphi

ds a

re s

een

in th

e flo

wer

s, e

nsur

e co

ntin

ued

prev

entiv

e re

leas

es.

At h

igh

infe

stat

ions

, the

hea

ds a

nd le

aves

bec

ome

dist

orte

d an

d th

ere

is a

n ac

cum

ulat

ion

of

hone

ydew

on

the

mat

urin

g fr

uit.

Con

trol

out

brea

ks w

ith th

e sa

me

stra

tegy

as

durin

g sp

ring.

In

the

pres

ence

of h

yper

para

sitis

m, u

se c

urat

ive

rele

ases

of A

phid

olet

es a

nd la

dybe

etle

s.

Fall

Nov (Sept. – .)

Mon

itor

mid

dle

to to

p of

can

opy

for

pres

ence

of

aph

ids

and

bio-

cont

rol a

gent

s. C

ontin

ue

mon

itorin

g un

til m

iddl

e of

Oct

ober

.

Sta

rtin

g fa

ll w

ith a

low

pop

ulat

ion

of g

reen

pea

ch a

phid

s an

d a

wel

l-est

ablis

hed

popu

latio

n of

pr

edat

ors

and

para

sito

ids

will

pre

vent

aph

id o

utbr

eaks

. Use

cur

ativ

e re

leas

es o

f lad

ybee

tles,

A

phid

olet

es a

nd A

phid

ius

spp.

for

cont

rol o

f lat

e ou

tbre

aks.


5.

Pest

an

d D

isease M

an

ag

em

en

t

Tab

le 5

-2.

Su

mm

ary

of

IPM

str

ateg

ies

for

the

foxg

love

, po

tato

an

d m

elo

n/c

ott

on

ap

hid

. S

easo

n

Sp

ecie

s

Mo

nit

ori

ng

C

on

tro

l Str

ateg

ies

Foxglove aphid

Mon

itor

plan

t hea

ds fo

r st

unte

d gr

owth

, def

orm

ed

leav

es a

nd c

ast s

kins

. T

hrou

ghou

t the

yea

r, w

atch

fo

r br

ight

yel

low

blo

tchi

ng o

n th

e lo

wer

leav

es, a

sig

n of

ea

rly in

fest

atio

n of

the

foxg

love

aph

id.

Ass

ess

A.

abdo

min

alis

and

Aph

idol

etes

po

pula

tions

and

adj

ust

rele

ases

acc

ordi

ngly

.

Infe

stat

ions

of t

he fo

xglo

ve a

phid

occ

ur o

nly

spor

adic

ally

on

gree

nhou

se p

eppe

rs a

nd p

reve

ntiv

e co

ntro

l is

rare

ly u

sed.

Con

trol

of s

mal

l hot

spo

ts c

onsi

stin

g of

a fe

w p

lant

s is

mos

t suc

cess

ful

whe

n th

e in

fest

ed p

lant

s ar

e fir

st tr

eate

d w

ith a

n in

sect

icid

al s

oap

follo

wed

by

intr

oduc

tions

of

A. a

bdom

inal

is, A

. erv

i and

Aph

idol

etes

in a

nd a

roun

d th

e in

fest

ed a

rea.

The

app

licat

ion

of

inse

ctic

idal

soa

p w

ill c

ause

som

e ph

ytot

oxic

ity o

n th

e pe

pper

folia

ge. I

t tak

es a

min

imum

of 3

w

eeks

for

A. a

bdom

inal

is a

nd A

. erv

i to

beco

me

effe

ctiv

e; k

illed

aph

ids

turn

into

bla

ck m

umm

ies

and

the

para

sito

ids

emer

ge a

fter

21 d

ays.

Onc

e es

tabl

ishe

d th

ey w

ill p

rovi

de e

ffect

ive

ongo

ing

cont

rol.

Ear

ly d

etec

tion

and

imm

edia

te a

pplic

atio

ns o

f con

trol

mea

sure

s in

crea

se th

e ch

ance

s fo

r su

cces

s.

If th

e fo

xglo

ve a

phid

infe

stat

ion

goes

und

etec

ted

and

expa

nds,

intr

oduc

e cu

rativ

e ra

tes

of A

. ab

dom

inal

is, A

. erv

i and

Aph

idol

etes

in a

nd a

roun

d th

e in

fest

ed a

rea

and

mon

itor

clos

ely

both

ap

hid

and

para

sito

id p

opul

atio

ns. C

hem

ical

con

trol

of t

he h

ot s

pots

sho

uld

be c

onsi

dere

d w

hen

blac

k m

umm

ies

or A

phid

olet

es la

rvae

are

few

or

cann

ot b

e fo

und

2-3

wee

ks a

fter

rele

ase.

C

hem

ical

con

trol

of t

he e

ntire

hou

se is

the

last

line

of d

efen

se a

nd s

houl

d be

app

lied

whe

n bi

olog

ical

con

trol

is n

ot w

orki

ng a

nd th

e si

ze a

nd n

umbe

r of

hot

spo

ts c

ontin

ues

to in

crea

se.

Potato aphid

Mon

itor

plan

t hea

ds fo

r de

form

ed g

row

th, c

ast s

kins

, up

war

d cu

pped

leav

es a

nd

exce

ssiv

e ho

neyd

ew

secr

etio

ns.

The

pot

ato

aphi

d is

a s

pora

dic

pest

and

pre

vent

ive

cont

rol i

s no

t rou

tinel

y us

ed. C

ontr

ol a

sm

all

hot s

pot u

sing

a s

imila

r st

rate

gy a

s fo

r th

e fo

xglo

ve a

phid

, usi

ng r

epea

ted

rele

ases

of A

phid

ius

ervi

. It

take

s a

min

imum

of 3

wee

ks fo

r A

. erv

i to

beco

me

effe

ctiv

e: 1

4 da

ys to

turn

into

m

umm

ies

and

an a

dditi

onal

7 d

ays

to e

mer

ge.

Use

the

sam

e co

ntro

l str

ateg

y as

abo

ve if

hot

spot

s go

und

etec

ted

and

expa

nd. T

he a

bsen

ce o

f A

. erv

i mum

mie

s an

d A

phid

olet

es la

rvae

2-3

wee

ks a

fter

intr

oduc

tion

can

just

ify c

hem

ical

con

trol

of

the

hot s

pot.

Winter (December - February)

Ma

elon/cotton phid

Mon

itor

the

mid

dle

and

top

of

cano

py a

nd w

atch

for

defo

rmed

gro

wth

, and

ex

cess

ive

hone

ydew

se

cret

ions

.

For

pre

vent

ive

cont

rol,

intr

oduc

e ba

nker

pla

nts

with

A. c

olem

ani o

r re

peat

ed r

elea

se o

f thi

s pa

rasi

toid

. For

cur

ativ

e co

ntro

l, tr

y re

peat

ed a

pplic

atio

ns o

f par

asito

ids

and

pred

ator

s.

Lady

beet

les

are

the

first

line

of c

ontr

ol. T

hey

shou

ld r

educ

e th

e ap

hid

popu

latio

n to

a

man

agea

ble

leve

l in

a sh

ort t

ime.

Aph

idol

etes

can

als

o be

effe

ctiv

e in

con

trol

ling

this

pes

t. It

will

ta

ke a

min

imum

of 3

wee

ks fo

r A

. col

eman

i to

beco

me

effe

ctiv

e. O

nce

esta

blis

hed

they

will

pr

ovid

e go

od c

ontr

ol fo

r th

e ne

xt fe

w w

eeks

.

Foxglove and potato a phid

Mai

ntai

n th

e sa

me

mon

itorin

g pr

ogra

m a

s in

win

ter.

M

onito

r fo

r w

inge

d ad

ults

in

the

flow

ers.

The

y si

gnal

an

influ

x of

aph

ids

from

out

side

. A

sses

s po

pula

tions

of

bene

ficia

ls in

the

gree

nhou

se

and

adju

st r

elea

ses

if ne

cess

ary.

Bio

logi

cal c

ontr

ol s

trat

egie

s fo

r sm

all a

nd la

rge

hot-

spot

infe

stat

ions

are

the

sam

e as

in th

e w

inte

r. A

phid

olet

es a

re a

goo

d ch

oice

at t

his

time

of th

e ye

ar.

The

y ar

e m

ore

effe

ctiv

e in

the

sprin

g an

d w

ill r

epro

duce

; Aph

idol

etes

atta

ck th

e ap

hid

with

the

leas

t dis

turb

ance

, red

ucin

g th

e ch

ance

of d

ispe

rsal

and

esc

ape

from

pre

datio

n. T

he u

se o

f che

mic

als

is n

ot r

ecom

men

ded

at

this

tim

e, a

s it

will

red

uce

or e

limin

ate

esta

blis

hed

bene

ficia

ls, s

peci

fical

ly O

rius.

Incr

ease

rel

ease

ra

tes

whe

n w

inge

d ap

hids

are

det

ecte

d in

the

flow

ers.

Spring (March – April)

Mcaphid

elon/otton

Mon

itorin

g is

the

sam

e as

in

the

win

ter.

P

reve

ntiv

e an

d cu

rativ

e co

ntro

l is

the

sam

e as

dur

ing

win

ter

and

relie

s on

rep

eate

d re

leas

es o

f la

dybe

etle

s, A

. col

eman

i and

Aph

idol

etes

.


5.

Pest

an

d D

isease M

an

ag

em

en

t

Foxglove aphid

Mon

itor

the

low

er-m

iddl

e

cano

py a

nd w

atch

for

yello

w

blot

ched

, sen

esce

d an

d dr

oppi

ng le

aves

. Loo

k fo

r si

gns

of h

yper

para

sitis

m.

Use

rep

eate

d ap

plic

atio

ns o

f Aph

idol

etes

, and

A. a

bdom

inal

is fo

r co

ntro

l of f

oxgl

ove

aphi

ds.

Dur

ing

sum

mer

the

tole

ranc

e fo

r fo

xglo

ve d

amag

e is

muc

h hi

gher

than

dur

ing

win

ter

or s

prin

g,

mos

tly b

ecau

se d

amag

e ca

used

by

low

infe

stat

ions

has

no

econ

omic

impa

ct.

Mai

ntai

n pr

even

tive

rele

ases

of A

phid

olet

es, a

nd A

. abd

omin

alis

whe

n in

fest

atio

ns a

re lo

w; a

pply

cur

ativ

e re

leas

e ra

tes

if in

fest

atio

ns in

crea

se.

Potato aphid

Mon

itor

the

low

er-

mid

dle

cano

py a

nd w

atch

for

yello

win

g an

d se

nesc

ing

leav

es w

ith la

rge

amou

nts

of

hone

ydew

. M

onito

r th

e pe

pper

flow

ers

for

the

pres

ence

of w

inge

d ap

hids

an

d lo

ok fo

r hy

perp

aras

itism

.

Bio

logi

cal c

ontr

ol d

epen

ds o

n re

petit

ive

rele

ases

of A

. erv

i and

Aph

idol

etes

. In

the

pres

ence

of

hype

rpar

asito

ids,

use

rep

eate

d re

leas

es o

f Aph

idol

etes

and

lady

beet

les.

Mai

ntai

n co

ntin

uous

pr

even

tive

rele

ases

in th

e pr

esen

ce o

f low

infe

stat

ions

; thi

s w

ill e

nsur

e ef

fect

ive

cont

rol o

f the

po

tato

aph

id d

urin

g su

mm

er a

nd p

reve

nt o

utbr

eaks

in th

e fa

ll.

Summer (May – August)

Mcotton a

elon/

phid

Mon

itor

mid

dle

to to

p of

ca

nopy

. Loo

k fo

r hy

perp

aras

itism

and

win

ged

adul

ts in

the

pepp

er fl

ower

s.

Pre

vent

ive

and

cura

tive

cont

rol i

s th

e sa

me

as d

urin

g w

inte

r or

spr

ing

and

relie

s on

rep

eate

d re

leas

es o

f lad

ybee

tles,

A. c

olem

ani a

nd A

phid

olet

es.

In th

e pr

esen

ce o

f hyp

erpa

rsito

ids

rely

on

Aph

idol

etes

and

lady

beet

les

for

both

pre

vent

ive

and

cura

tive

cont

rol.

Effe

ctiv

e co

ntro

l of t

he

mel

on/c

otto

n ap

hid

in th

e su

mm

er w

ill h

elp

prev

ent o

utbr

eaks

in th

e fa

ll.

Foxglove aphid

Mon

itor

mid

dle

to lo

w c

anop

y.

Alth

ough

pre

sent

in th

e cr

op, f

oxgl

ove

aphi

d ra

rely

incr

ease

s to

out

brea

k le

vels

in th

e fa

ll.

Paphid otato

Mon

itor

low

to m

iddl

e ca

nopy

. Lo

ok fo

r ye

llow

ing

and

sene

scin

g le

aves

and

ho

neyd

ew d

epos

its.

Use

cur

ativ

e re

leas

es o

f A. e

rvi,

Aph

idol

etes

and

lady

beet

les

to c

ontr

ol o

ccas

iona

l out

brea

ks.

Fall (September –Nov.)

Melon/ cotton aphid

Mon

itor

mid

dle

to to

p of

ca

nopy

. U

se th

e sa

me

cont

rol s

trat

egy

as in

the

sum

mer

.

Tab

le 5

-2.

(Co

nt’

d)

Su

mm

ary

of

IPM

str

ateg

ies

for

the

foxg

love

, po

tato

an

d m

elo

n/c

ott

on

ap

hid

.


5.

Pest

an

d D

isease M

an

ag

em

en

t

Tab

le 5

-3. C

om

mer

cial

ly a

vaila

ble

bio

log

ical

co

ntr

ol a

gen

ts f

or

aph

id c

on

tro

l

Nam

e

Ap

pea

ran

ce a

nd

life

cyc

le

Ap

plic

atio

ns

Adu

lts h

ave

5-7m

m lo

ng s

lend

er, b

lack

bod

y. F

emal

es la

y on

e eg

g in

an

aphi

d, c

ausi

ng it

to s

wel

l and

cha

nge

colo

ur to

a y

ello

wis

h-br

own.

The

pa

rasi

tized

aph

id is

cal

led

a “m

umm

y”. T

he a

dult

was

p ex

its th

e m

umm

y th

roug

h a

smal

l, ro

und

hole

.

Lif

e cy

cle

at 2

0 OC

(68

oF

) E

gg to

adu

lt

13 d

ays

Fec

undi

ty

30

0 eg

gs/fe

mal

eLo

ngev

ity o

f adu

lt

6 da

ys

Parasitic wasp Aphidius colemani

Aphidius matricariae

Sex

rat

io

50-6

0% fe

mal

es

Tar

get h

ost o

f A. c

olem

ani i

s th

e m

elon

aph

id, b

ut it

will

als

o pa

rasi

tize

the

gree

n pe

ach

aphi

d. B

oth

para

sito

ids

have

exc

elle

nt s

earc

hing

abi

lity

and

can

be u

sed

prev

entiv

ely

at lo

w p

est i

nfes

tatio

n le

vels

. Hyp

er-p

aras

ites

can

redu

ce e

ffica

cy o

f thi

s pa

rasi

toid

. R

elea

se r

ate

(per

m2 )*

: P

reve

ntiv

e

L

ow to

med

ium

infe

stat

ions

M

ediu

m to

hig

h in

fest

atio

ns

0.1-

0.25

1.

0

1-5

Min

imum

of 2

-3 in

trod

uctio

ns, 7

-14

days

apa

rt.

Adu

lts a

re 4

-5 m

m lo

ng a

nd b

lack

in c

olou

r. M

umm

ies

are

sim

ilar

to

thos

e of

A. c

olem

ani.

Lif

e cy

cle

at 2

0 OC

(68

oF

) E

gg to

mum

my

13.5

day

s E

gg to

adu

lt 2

0 da

ys

Fec

undi

ty

Not

ava

ilabl

e

Parasiticph

wasp Aidius ervi

Long

evity

of a

dult

N

ot a

vaila

ble

Tar

get h

ost i

s th

e po

tato

and

foxg

love

aph

id, b

ut it

will

als

o pa

rasi

tize

the

gree

n pe

ach

aphi

d. L

ike

A. c

olem

ani,

has

exce

llent

sea

rchi

ng a

bilit

y an

d ca

n be

use

d pr

even

tivel

y at

low

pes

t inf

esta

tions

. Effe

ctiv

enes

s ca

n be

re

duce

d by

hyp

er-p

aras

itism

. R

elea

se r

ates

(pe

r m

2 ):

Pre

vent

ive

Low

to m

ediu

m in

fest

atio

ns

Med

ium

to h

igh

infe

stat

ions

0.2-

0.5

0.

5-1.

0

1.

0-5.

0 M

inim

um o

f 2-3

intr

oduc

tions

, 7-1

4 da

ys a

part

. A

dults

are

2.5

-3 m

m lo

ng, h

ave

a bl

ack

thor

ax a

nd a

yel

low

abd

omen

. P

aras

itize

d ap

hids

turn

into

bla

ck m

umm

ies.

L

ife

cycl

e at

20

OC

(68

oF

) E

gg to

mum

my

7 da

ys

Egg

to a

dult

21 d

ays

Fec

undi

ty

270

eggs

/fem

ale

Parasitic wasp Aphelinus abdominalis

See colour photos 17 & 18.

Long

evity

of a

dult

19 d

ays

Fav

oure

d ho

sts

are

pota

to a

nd fo

xglo

ve a

phid

s. It

can

als

o pa

rasi

tize

the

gree

n pe

ach

aphi

d. T

hese

was

ps a

re n

ot v

ery

mob

ile, s

o re

leas

e sh

ould

be

mad

e on

and

aro

und

the

infe

sted

pla

nts.

Effe

ctiv

enes

s ca

n be

red

uced

by

hyp

erpa

rasi

tism

. R

elea

se r

ates

(pe

r m

2 ):

Pre

vent

ive

Lo

w to

med

ium

infe

stat

ions

M

ediu

m to

hig

h in

fest

atio

ns

not

adv

ised

1-5

5-

10

Tw

o w

eekl

y in

trod

uctio

ns in

infe

sted

are

as o

nly.


5.

Pest

an

d D

isease M

an

ag

em

en

t

Tab

le 5

-3.

(Co

nt’

d)

Co

mm

erci

ally

ava

ilab

le b

iolo

gic

al c

on

tro

l ag

ents

fo

r ap

hid

co

ntr

ol

Adu

lt m

idge

(fly

) is

2.5

mm

long

and

has

a fr

agile

bod

y w

ith lo

ng le

gs

and

long

ant

enna

e. F

ully

-gro

wn

larv

ae a

re 2

.5 m

m lo

ng a

nd y

ello

w-

oran

ge in

col

our.

Egg

s ar

e ve

ry s

mal

l, ov

al-s

hape

d an

d sh

iny

oran

ge-

red

in c

olor

. The

y ar

e la

id in

clu

ster

s am

ong

colo

nies

of a

phid

s.

Lif

e cy

cle

at 2

1 OC

(70

oF

) E

gg to

adu

lt 3.

5 w

eeks

F

ecun

dity

100-

150

eggs

/fem

ale

Long

evity

of a

dult

10 d

ays

Dev

elop

men

tal s

tage

s E

gg, l

arva

, pup

a, a

dult

Predatory midge A phidoletes aphidimyza

Pre

daci

ous

stag

es

Larv

al s

tage

Thi

s pr

edat

or w

ill p

rey

on m

any

aphi

d sp

ecie

s. It

has

goo

d se

arch

ing

abili

ty a

nd is

ver

y ef

fect

ive

at h

igh

popu

latio

ns o

f aph

ids.

Aph

idol

etes

has

a

diap

ause

sta

ge, a

nd c

an b

e us

ed e

ffect

ivel

y fr

om m

id-M

arch

to m

id-

Sep

tem

ber.

It c

an b

e re

leas

ed e

arlie

r; th

e fir

st g

ener

atio

n w

ill c

ontr

ol

aphi

ds b

ut w

ill n

ot r

epro

duce

. The

y re

quire

a la

yer

of d

irt fo

r pu

patio

n an

d ca

n’t c

ompl

ete

the

life

cycl

e in

gre

enho

uses

with

pla

stic

floo

r co

verin

g un

less

a fi

ne la

yer

of s

awdu

st o

r sa

nd is

add

ed to

the

floor

. The

pre

dato

ry

mite

, Am

byse

sis

dege

nera

ns fe

eds

on A

phid

olet

es e

ggs,

red

ucin

g ef

ficac

y.

Rel

ease

rat

es (

per

m2 ):

P

reve

ntiv

e L

ow to

med

ium

infe

stat

ions

Med

ium

to h

igh

infe

stat

ions

0

.25-

0.5

pup

a

1

.0-5

.0 p

upae

10

pup

ae

Min

imum

of 3

intr

oduc

tions

, 7 d

ays

apar

t. A

dults

are

5 m

m lo

ng, o

rang

e-br

own

with

bla

ck s

pots

. Lar

vae

are

blac

k w

ith y

ello

wis

h-or

ange

spo

ts. E

ggs

are

oval

, yel

low

, and

laid

in c

lust

ers

amon

g ap

hid

colo

nies

. Lif

e cy

cle

at 2

2 OC

(72

oF

) E

gg to

adu

lt 25

-31

days

F

ecun

dity

10-5

0 eg

gs/fe

mal

e/da

yLo

ngev

ity o

f adu

lt N

ot a

vaila

ble

Dev

elop

men

tal s

tage

s E

gg, l

arva

, pup

a, a

dult

L ady beet

onvergens

leHippodemia c

See colour photo 22.

Pre

daci

ous

stag

es

Adu

lt an

d la

rval

sta

ges

Lady

bee

tles

will

pre

y on

man

y ap

hid

spec

ies.

The

y ar

e us

ed m

ainl

y as

a

corr

ectiv

e m

easu

re, t

o qu

ickl

y re

duce

hig

h ap

hid

infe

stat

ions

. Qua

lity

of

this

pre

dato

r is

inco

nsis

tent

and

they

can

be

infe

sted

with

par

sito

ids.

R

elea

sing

too

man

y la

dybi

rds

can

jeop

ardi

ze th

e po

pula

tion

build

up o

f be

nefic

ial p

aras

itic

was

ps.

Rel

ease

rat

es (

per

m2 ):

P

reve

ntiv

e L

ow to

med

ium

infe

stat

ions

Med

ium

to h

igh

infe

stat

ions

n

ot a

dvis

ed

25

50

One

intr

oduc

tion

in in

fest

ed a

reas

onl

y.

Adu

lts a

re 5

-8 m

m in

leng

th a

nd h

ave

a ch

arac

teris

tic “

M”

shap

ed w

hite

pa

ttern

on

the

shou

lder

s. C

olou

r ca

n va

ry fr

om b

lack

to r

ed.

Lif

e cy

cle

at 2

5 OC

(77

oF

) E

gg to

adu

lt 16

day

s F

ecun

dity

20 e

ggs/

fem

ale/

day

Long

evity

of a

dult

2 m

onth

s D

evel

opm

enta

l sta

ges

Egg

, lar

va, p

upa,

adu

lt

Lady beetle Harmonia axyridis

Pre

daci

ous

stag

es

Larv

al s

tage

s an

d ad

ults

Alth

ough

this

pre

dato

r fe

eds

on m

any

aphi

d sp

ecie

s its

rol

e in

bio

logi

cal

cont

rol i

s no

t yet

cle

ar. C

urre

ntly

it is

too

expe

nsiv

e to

be

cons

ider

ed fo

r fu

ll-sc

ale

com

mer

cial

rel

ease

s an

d is

rel

ease

d in

isol

ated

aph

id h

ot s

pots

R

elea

se r

ates

: P

reve

ntiv

e

Low

to m

ediu

m in

fest

atio

ns

Med

ium

to h

igh

infe

stat

ions

n

ot a

dvis

ed

1

larv

a/10

0 ap

hids

1

larv

a/ 5

0 ap

hids

O

ne in

trod

uctio

n in

infe

sted

are

as o

nly.

Adu

lts a

re a

bout

12

mm

long

. Bot

h ad

ults

and

larv

ae h

ave

big

pinc

er-li

ke

mou

ths.

L

ife

cycl

e at

20

OC

(68

oF

) E

gg to

adu

lt 25

-35

days

F

ecun

dity

20

0-40

0 eg

gs/fe

mal

e

Long

evity

of a

dult

50-8

0 da

ys

Dev

elop

men

tal s

tage

s E

gg, l

arva

, pup

a, a

dult

L acewing

hrysopa spp.

sChrysoperla and C

Pre

daci

ous

stag

es

Larv

al s

tage

The

se p

reda

tors

feed

on

man

y ap

hid

spec

ies

and

soft

bodi

ed in

sect

s an

d m

ites.

Dia

paus

e lim

its u

se o

f thi

s sp

ecie

s to

spr

ing

and

sum

mer

. Pol

len

is

requ

ired

for

lace

win

gs to

mat

ure

and

repr

oduc

e.

Rel

ease

rat

es (

per

m2)

: P

reve

ntiv

e Lo

w to

med

ium

infe

stat

ions

Med

ium

to h

igh

infe

stat

ions

n

ot a

dvis

ed

10

larv

ae

20

larv

ae

Intr

oduc

e w

eekl

y in

infe

sted

are

as u

ntil

cont

rol i

s ac

hiev

ed.

*- R

elea

ses

rate

s pr

esen

ted

in th

e ta

ble

are

for

gene

ral g

uida

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Effects of Infestation Levels andSeasonal Changes in TemperatureDistribution of aphids within the pepper canopydepends primarily on the infestation level but isalso affected by seasonal changes in temperature.

At high infestation levels aphids are foundthroughout the pepper canopy, irrespective ofgrowing season. This is true for all four speciesfound on peppers.

At low infestation levels distribution of thefoxglove, potato and green peach aphid withinthe pepper canopy changes in response to tem-perature. During winter they are found at thetop of the canopy; during summer, they arefound typically in the lower canopy. The melonaphid is not affected by changes in temperatureand at low infestation levels, it is found in themid- to upper canopy.

Effects of Aphid Feeding on DifferentCanopy LevelsTop canopy (in the head)

Feeding on the top of the canopy stunts thegrowth of the pepper plant, prevents fruit setand reduces the marketability of the maturingfruit due to honeydew deposition. Growth ofsooty mould can also reduce photosynthesis.

Mid-canopy

Feeding on the middle of the pepper canopydeposits honeydew secretions on the maturingfruit and leaves. This reduces the marketabilityof the mature fruit. Although labour-intensiveand thus costly, the honeydew residue can beremoved by washing.

Low canopy

During summer the green peach, foxglove, andpotato aphids feed in the low canopy below thematuring fruit. At low infestations feeding hasno direct economic impact on pepper produc-tion. This should not be interpreted as an indi-cation to ease off the preventive control. Leftuncontrolled, low infestations of aphids pose ahigh risk for a population outbreak, especially inthe presence of hyperparasites. Maintenance ofpreventive controls during this time of the year

is critical to the successful biological control ofaphids during late summer and fall.

Impact of the Nature and Location ofFeeding Damage on the Pepper PlantEach aphid species inflicts different types anddegrees of damage depending on plant age andfeeding location within the canopy.

Foxglove aphid: Saliva injected during feedingcauses a hyper-toxic reaction. Feeding in theheads causes discolouration, wrinkling or foldingof leaves and distortion of new growth. Feedingon the pepper head by even a small numbers offoxglove aphids can cause growth stunting andfruit abortion. Feeding on lower leaves cancause bright yellow blotching, senescing anddefoliation. See colour photo 23.

Potato aphid: Saliva injected during feedingcauses a hyper-toxic reaction resulting in dis-torted leaves and stems, stunted plants andnecrotic spots on leaves. This aphid also se-cretes a large amount of honeydew. Althoughless damaging than the foxglove aphid, feedingon the head by relatively low numbers of potatoaphids slows its growth. See colour photo 24.

Green peach aphid: Feeding by large numberscan cause leaf curling, distortion anddiscolouration, and in excessive numbers canultimately cause death of the head. Feeding inthe mid-canopy can reduce the marketability ofthe fruit due to honeydew secretion. See colourphoto 25.

Melon/cotton aphid: Feeding by large numbersof aphids can cause growth deformations andleaf distortion and curling. Even at lowpopulations, melon/cotton aphids can secretelarge amounts of honeydew on the leaves andmaturing fruit.

Dispersal and Colony StructureThe four aphids have different dispersal behav-iour and colony structures. Dispersal behaviourinfluences the choice of bio-control agents andcultural practices. Different colony structuresaffect the amount of secreted honeydew.


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DispersalWhen disturbed, foxglove and potato aphidsdisperse by fast walking and by dropping fromthe leaves. This behaviour helps them avoidpredators. As a result, they tend to spreadthroughout the greenhouse when disturbed bygreenhouse staff or by inappropriate choice ofa bio-control agent. Minimize their dispersal by:

Specific crop maintenance in foxglove aphid

infested area: Collect prunings into closedcontainers and remove from the greenhouse toprevent further dispersal. Remove all senescentleaves and debris from the greenhouse floor.Aphids concealed under leaves and debris willnot be affected by fumigants or natural enemies.

Choice of bio-control agents: Use Aphidoletes

to control foxglove and potato aphids. Theycause fewer disturbances than other predatorsand parasitoids. Aphelinus abdominalis andAphidius ervi can also be used without causingexcessive foxglove or potato aphid dispersal.Use of ladybugs alone should be avoided.

Colony StructureThe more aphids per colony the more honey-dew they will produce per unit of leaf area.

At low to medium infestation levels, foxglove andpotato aphids form small, spread-out colonies onboth upper and lower leaf surfaces. At highinfestation levels, both aphids tend to cluster.

Irrespective of infestation levels, green peachand melon aphids tend to cluster on the under-side of pepper leaves and produce a largeamount of honeydew.

Chemical Control of AphidsBefore using pesticides for control of aphids orother pests, read the cautions on page 78 andon the label. For more information on any ofthe chemicals, see page 147.

Diazinon 500E

Use 230 mL/250L of water for 4,000 m2

(575mL/625L of water / ha). For peppersdiazinon may affect flower bud development soit is only recommended for use before flowering

or after last set. This product will disrupt bio-controls except some strains of Phytoseiulus

persimilis. Avoid contact with heating pipes, asvaporized diazinon will kill bio-control agents.Do not apply within 5 days of harvest.

Intercept 60 WP (imidacloprid)

Impower is a chloronicotinyl that combinessystemic activity with long residual control ofaphids and whiteflies. It has no effect on spidermites. It is not used as a foliar spray but as asoil drench to actively growing plants withestablished root systems. It is translocatedupwards in the plant. Use calibrated drip, hand-held or motorized irrigation equipment to applythe soil drench. For best results, do not leachmedia for 10-14 days after application. It isharmful to Aphidius and Aphidoletes. Effect onother beneficials is unknown. It has moderateacute mammalian toxicity. It is highly toxic toaquatic invertebrates. Do not apply within 2

days of harvest.

Nicotine Smoke

Use 1 can/300m3, spacing the fumigatorsthroughout the greenhouse. Only one applica-tion is allowable per planting. The greenhouseshould be tightly closed and temperature main-tained at 22 – 25ºC. If a circulating fan ispresent in the greenhouse, it should be turnedon for about 15 minutes to ensure uniformdistribution. Warning: Nicotine smoke is

extremely hazardous. Use a full facemaskwith approved canister and protective clothingwhen entering a greenhouse that is still beingventilated. Supplied air must be used if there isa risk of exposure to the smoke. Ventilate thegreenhouse thoroughly the day after fumigation.Do not apply within 5 days of harvest.

Safer’s Insecticidal Soap

Use 20 mL/L of water. Insecticidal Soap actsonly by direct contact so thorough coverage isessential. Phytotoxicity can occur if the labelrate is exceeded or if applied in direct sunlight.Use high pressure and very fine droplet size. Donot apply more than twice per crop cycle. Do

not apply within 3 days of harvest.


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Thiodan 4E (endosulfan)

Use 1.25 - 1.5 mL/L of water. Thoroughcoverage of undersides of leaves is essential.Do not apply more than twice per season. Thisproduct is highly toxic to the majority of bio-logical control agents and makes growersdependent on chemicals for the control ofsubsequent pest outbreaks. It also has highmammalian toxicity. Do not apply within 2

days of harvest.

Trounce (insecticidal soap and pyrethrin)

Use 50mL/L of water. Insecticidal soap actsonly by direct contact so thorough coverage isessential. Phytotoxicity can occur if the labelrate is exceeded or if applied in direct sunlight.Do not apply within 5 days of harvest.

Cleanup using Dibrom (naled)

Dibrom can only be used during end-of-seasoncleanup, in an empty greenhouse. Use 10mL/100m2 of greenhouse space when applyingDibrom to the heating pipes. Apply undilutedliquid to evenly spaced coldpipes. Do not allowDibrom to drip from thepipes onto the floor as itwon’t completely volatilizeon the floor. Immediatelyheat the pipes to at least41°C and keep vents closedfor at least 3 hours after thepipes are hot. Keep thegreenhouse closed over-night following applicationand ventilate thoroughlybefore entering.

Fungus Gnats

TaxonomyFungus gnats, Bradysia spp., shore flies, mothflies, crane flies and mosquitoes are closelyrelated flies, world-wide in occurrence. Onespecies of fungus gnat, common in New Zea-land, has luminous stages that glow in the darkand are known as glowworms. Fungus gnats,shore flies and moth flies are very common inpepper greenhouses. Similar in appearance theyall thrive under moist conditions in the pres-ence of abundant organic debris and algae.Shore and moth flies are considered harmless ornuisance pests. However, they have beenknown to transmit Fusarium and should not betolerated at high numbers. Fungus gnats areharmful to roots of pepper plants and it isimportant to distinguish them from shore andmoth flies (see Figure 5-3).

Figure 5-3. Adult and larva of the fungus gnat, shore fly and moth fly.

Source: University of California, Agriculture and Natural Resources.

Publication 7448. Revised August 2001. 6 pp.

Fungus gnat Shore fly Moth fly

A

du

lt

Adults are 2-3 mm long, delicate and mosquito like with long legs and antennae. The wings are white-gray to clear with a characteristic Y-shaped vein.

Adults are 2-4 cm long, robust and dark with bristle-like antennae that are shorter than the head. Each grayish wing has five pale spots.

Adults are about 3 mm long and densely covered with dark or gray hairs.

Lar

va

Larvae are 4 mm long, whitish to clear, with a shiny black head capsule.

Larvae have no distinct head capsule. They can be opaque yellowish, whitish or brown, with a forked air tube at their rear end.

Larvae can be whitish, gray, or brownish with a distinct but a small and flattened head.


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Appearance and Life Cycle ofFungus GnatsAdults are weak flyers and are often seenresting on the media or leaf surfaces. Fungusgnats lay clusters of eggs in moist media.Larvae pass through four stages and feedmostly on fungal mycelium, algae, root hairsand decaying matter.

Life cycle at 24 ºC (75 ºF)

Egg to adult 21 days

Fecundity 75 - 200 eggs/female

Longevity of adult 3 - 5 days

Developmental stages Egg, 4 larvalstages, pupa andadult

DamageFungus gnat larvae feed on pepper root tissueand cause damaged root tissue to swell. Severelarval damage can reduce plant growth. Feedingwounds provide entry sites for root pathogenssuch as Pythium, Fusarium and Phytophthora.

Adults can also transfer these diseases but theyare relatively week vectors.

MonitoringAdult flies are attracted to yellow sticky trapsmaking them useful for monitoring and masstrapping of adults. Position the traps horizon-tally, approximately 30 cm above the slab tomass-trap adults. Position a minimum one cardper 1000 m2 above the canopy to monitoradults. If a trap catches more than 50 adults perweek, consider the application of treatments.

Potato disks and emergence traps can be usedto monitor larval and adult stages.

Place a 2.5 cm-thick disk of potato halfimbedded into media. Use at least 10 disks per1000 m2. Examine the disks and the mediaunderneath weekly for the presence of larvae.Change the potato disks about every 2 weeks.

Place inverted plastic cups over the media.

Count and examine the emerged adults. Thepresence of fungus gnat larvae or adults indi-cates that the media is infested and may justifytreatment.

Cultural ControlKeep the greenhouse floor dry and clean byavoiding over-watering, eliminating waterpuddles and minimizing plant debris on thegreenhouse floor. Well-managed drain collec-tion and good sanitation will keep thepopulations of fungus gnats below the eco-nomic threshold.

Biological ControlStart releases of the predatory mite, Hypoaspis

spp., during propagation and repeat soon afterplanting. Young plants are most susceptible todamage. Use nematode applications for curativecontrol of fungus gnat larvae (see Table 5-4).

Microbial ControlBacillus thuringiensis var. israeliensis

(VectoBac 600L)

Bti is a microbial larvicide based on toxinsproduced by the bacterium, B. thuringiensis var.israeliensis. The product is formulated as anaqueous suspension and must be eaten by thefungus gnat larvae to cause toxic effects; there isno contact activity. Thorough coverage is essen-tial. Apply VectoBac 600L as a soil drench withadequate water to sufficiently wet the surfacewhere larvae are found. Apply weekly as adrench when pest monitoring indicates the need.VectoBac can be used up to harvest.

Application rates:

Light to moderate infestation, use 2 to 4 L/1000 L water applied as a drench. Heavyinfestation, use 4 to 8 L/1000 L water. Suc-cessful control is indicated by less than 50adults caught per sticky trap per week.

Chemical ControlThere are currently no registered chemicalcontrol options for fungus gnats on greenhousesweet pepper.


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Loopers

TaxonomyLooper larvae are caterpillars with legs in frontand back which gives them a looping or ‘meas-uring worm’ appearance while walking. Theybelong to the order Lepidoptera which includestrue moths and butterflies. Of concern to thegreenhouse industry is the cabbage looper,Trichoplusia ni, a migratory pest from southernUSA. Winter temperatures in B.C. appear toocold for the loopers to over-winter outdoors butpopulations of loopers often survive green-house cleanup.

Appearance and Life CycleThe adult moth is brownish-grey with a charac-teristic silvery-white spot resembling the number“8” near the center of the forewing. The eggs aresmall, round greenish-white and laid singly onthe lower leaf surface. The larvae are pale greenwith white stripes on each side and along theback. See colour photo 26. When fully devel-

oped larvae are about 3 cm long. The maturecaterpillar spins a gauzy cocoon on the plant andpupates inside.

Life cycle at 21 OC (70oF)


Fecundity >1000 eggs/female

Longevity of adult 2 to 3 weeks

Developmental stages Egg, 5 larvalstages, pupa andadult

The eggs hatch after 2-5 days depending on thetemperature and the tiny larvae begin to feed.The larvae develop for 2 to 3 weeks, consum-ing progressively more plant tissue as they grow.Pupation occurs and the adults emerge in 10 to14 days. The moths live approximately 2 weeksand the females oviposit from a few to severalhundred eggs.

Name Appearance and life cycle

Pre

dat

ory

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Hyp

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H

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These mites are 1 mm long and light brown. During larval and first nymphal stages, they are white. They feed on fungus gnat eggs and larvae. They do not enter diapause, and can be used throughout the year. They also survive as scavengers, feeding on algae and plant debris. Hypoaspis are most effective when released preventively. Release rate*: preventive 50 -100/m2; released twice, one week apart.

P

red

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ove

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e

Ath

eta

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This beetle is 3.7 mm long, shiny, dark brown-black and covered with hair. It preys on all developmental stages of soil insects, including fungus gnats, shore flies, moth flies and thrips. At 25oC, it takes approximately 3 weeks to develop from egg to adult. Adult females lay about 8 eggs a day and live for 3 weeks. The beetles pass through an egg, 3 larval and a pupal stages before becoming adults. All larval and adult stages are predacious. It does not enter diapause and can be released throughout the year. Release rate*: 2 beetles/m2.

N

emat

od

es

Ste

iner

nem

a fe

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This species is the most effective nematode against fungus gnats. Adult and larval nematodes are small (1-1.5 mm long), elongated and unsegmented worms. They can be applied through the irrigation system. Nematodes will actively search for the larvae of soil insects. They reproduce inside the invaded host and once established can provide control throughout the season. Fungus gnat larvae turn from clear white to milky white when they have been infected by nematodes. High humidity content of the soil and soil temperature of 13-25 OC are required for the nematodes to be effective. Release rates*: curative 500,000/m2. Apply once at low infestation levels; repeat 14 days later at high infestation levels.

* - Release rates presented in this table are general guidelines only.

Table 5-4. Commercially available biological control agents for fungus gnats


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Feeding Symptoms and Egg LayingPatternThe larva is the damaging stage of this insect.The newly hatched larvae feed on the under-side of the leaf, often by removing a thin layerof tissue. This produces “windows” in theaffected leaves. Older caterpillars feed on theentire foliar tissue and can cause severe defolia-tion. Occasionally they will feed on the fruitcalyx resulting in an unmarketable product. Seecolour photo 27.

On peppers, loopers lay eggs singly, mostly atthe top of the canopy. Egg parasitoids forlooper control should be chosen based on theirability to search and parasitize eggs at the topof the canopy.

MonitoringPheromone traps (2/ha) can be used to detectthe presence of moths. Infestation levels and the

effectiveness of biological and chemical controlcan be determined by monitoring foliage in theupper canopy. Lack of new damage on upperleaves indicates effective control.

Biological Control with InsectsSee Table 5-5 for description of the two mainbiocontrol insects available against loopers.Start releasing Trichogramma once flying mothshave been observed. Control of looper out-breaks also depends on repeated releases of‘podi-bugs’ and repeated applications of micro-bial agents (Bt). Orius insidiosus and Dicyphus

hesperus have also been seen to feed occasion-ally on eggs and the smallest larval stage.Although they can contribute to the control ofloopers they can’t control outbreaks on theirown.

Table 5-5. Commercially available biological control agents for cabbage looper

Name Appearance, life cycle and release strategies

Parasitic wasps Trichogramma pretiosum, T. brassicae

Trichogramma are small (<1mm) parasitic wasps. Female wasps lay their eggs in the eggs of the cabbage looper and other moth species invading the greenhouse. A parasitized egg turns black in 7-10 days and an adult wasp emerges after another week. The wasps can parasitize from 50 to 80% of the looper eggs, but that alone cannot control the looper population. Trichogramma is a poor flier and disperses a maximum of 10 meters from the release point. An effective release pattern should include a minimum of 155 release points per ha. Under warm, summer conditions, both the wasp and the egg are very short lived; the wasp lives 2 to 4 days and the cabbage looper eggs hatch within 2-3 days. Control of cabbage loopers with Trichogramma requires frequent releases (twice a week) or use of extended-hatch cards. Release rates (females/m2)*: Preventive Low to medium infestations Medium to high infestations

5 10 20-40

Spined soldier bug or ‘Podi-bug’ Podisus maculoventris

Adult bugs are large (>1cm), robust insects, with yellow-brown body colouration and characteristic spined shoulders. Adults and immature ‘podi-bugs’ feed on all caterpillar stages. Successful establishment requires the presence of caterpillars and takes a relatively long period (10-12 weeks). Once established, this predatory bug is very effective in controlling cabbage loopers and other caterpillars for the rest of the season. Current release recommendations suggest 1 insect per plant in low infestation areas and 5-10 insects per plant in high infestation areas.

Parasitic wasp Cotesia marginiventris

Cotesia is a parasitic wasp that lays eggs inside first and second larval stages. This insect has been shown experimentally to cause substantial mortality of cabbage loopers in vegetable greenhouses but is not currently commercially available.

Orius insidiosus and Dicyphus hesperus have been seen to feed occasionally on eggs and the smallest larval stage. Although they can contribute to the control of loopers they can’t control looper outbreaks on their own.


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Biological Control with Microbials

Bacillus thuringiensis var. kurstaki(Dipel 2X, Foray 48BA)

Btk targets the larval stage of loopers and isavailable in two formulations, Dipel 2X (dryflowable) and Foray (low volume aqueousconcentrate). Note that the 2X formulation ofDipel cannot be applied as a dust. Both can beused up to harvest. Dipel or Foray should beapplied at the first appearance of larvae, as it ismore effective on the young larval stages. Thisproduct is sensitive to UV light and its efficacydecreases with storage time. Best results areaccomplished when fresh product is applied atthe end of the day. Effective control of cabbagelooper larvae depends on repeated applicationsand good coverage of the upper and lower leafsurface. The caterpillars must eat the treatedfoliage to be controlled. Application rates:

• Apply Dipel 2X at 75 to 150 g in 250 Lwater/4000 m2;

• Apply Foray 48BA at 60 to 180 mL/1000m2,(0.8 – 1.8 L/ha).

Control with Light TrapsLight traps can be used to attract and killmoths. Position a container with a soap solu-tion underneath each trap to collect and drownadults that survived impact with the light trap.Position traps where adults are observed (highlight areas, e.g. sidewalls). Use of light traps isnot recommended during the looper flightseason as they may attract insects from outsidethe greenhouse.

Chemical Control

Confirm (tebufenozide)

Use 500mL in 4,000L water/ha. Good spraycoverage is essential for control as the caterpil-

lars must eat the treated foliage. Do not exceed4 applications per year. Note: There is someevidence that tebufenozide may impact devel-opment of certain biological control agentssuch as Orius and ladybug larvae. It is recom-mended that growers monitor Orius populationscarefully and if populations are high, consideran alternative product such as Btk, since Orius

is known to feed on caterpillar eggs. Do not

apply within 3 days of harvest. Re-entry

period is 12 hrs.

Trounce (Safer’s insecticidal soap plus

pyrethrin)

Use 50m/L of water. Insecticidal Soap actsonly by direct contact so thorough coverage isessential. Phytotoxicity can occur if the labelrate is exceeded. Do not apply within 5 days

of harvest.


Fall cleanup should target, among other pests,adult moths and looper pupae to prevent carry-over into the new crop. Dibrom provides aneffective control of cabbage looper populationsalthough occasionally the pupal stage maysurvive a Dibrom application. A thorough powerwashing can remove most of the looper pupaefound on screens, pipes, posts and hooks.

Dibrom can only be used during end-of-seasoncleanup, in an empty greenhouse. Use 10mL/100m2 of greenhouse space when applyingDibrom to the heating pipes. Apply undilutedliquid to evenly spaced cold pipes. Do notallow Dibrom to drip from the pipes onto thefloor as it won’t completely volatilize on thefloor. Immediately heat the pipes to at least41°C and keep vents closed for at least 3 hoursafter the pipes are hot. Keep the greenhouseclosed over-night following application andventilate well before entering.


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Lygus Bugs

TaxonomyLygus bugs are members of the plant bugfamily, Miridae. It is a large and importantfamily containing many crop-damaging speciesincluding the tarnished plant bug, L. pratensis

and also several predacious species. Three lygusspecies, L. shulli, L. elisus, and L. hesperus causeeconomic loss to greenhouse peppers in theLower Fraser Valley of B.C.

Stink bugs, in the genus Euschistus, have occa-sionally been found on greenhouse peppers inB.C. Symptoms of feeding damage includedistinctly round and lighter than skin colourpatches on the fruit. Although damaged fruit isunmarketable infestations have not been greatenough to cause economic damage. Careshould be taken to distinguish the bug from thesimilar spined soldier bug, Podisus maculiventris,(see colour photo 29) used for biocontrol andto distinguish the damage from that caused bythe lygus bug.

Appearance and Life Cycle ofLygus BugThe adult bug is 6 to 6.5 mm long, and greenishor brownish with a characteristic yellow “V”marking on its triangular wing bases. See colourphoto 28. The eggs are imbedded into softplant tissue such as petioles or the midribs ofleaves. The eggs hatch to nymphs in 7 to10days depending on temperature. Nymphs gothrough 5 stages (instars). The nymphs resem-ble aphids, but have more robust legs, movefaster and are never found in groups.

The flight season of lygus bugs starts in March,when over-wintering adults begin to disperse,and lasts through to October. They can entergreenhouses anytime during the flight season.

Life cycle at 20 OC (68oF)

Egg to adult 30-35 days

Fecundity 50-150 eggs/female

Longevity of adult 10-12 weeks

Developmental stages Egg, five nym-phal stages andadult

Feeding DescriptionLygus bugs feed by repeatedly piercing andsucking the plant tissue. They excrete salivacontaining a blend of enzymes into the tissue.The enzymes break down cell walls and aid inthe removal of nutrients from the plant tissue.The growth deformations and stunting caused bylygus feeding is caused in part by the enzymesinterfering with the wound healing process.

Damage on PeppersOn greenhouse peppers, lygus bugs feed prefer-entially on flower parts, fruit and terminal andlateral tips. Work to date in B.C. indicates thatsymptoms of lygus damage vary within thegrowing season. In spring and early summer,lygus feeding results in growth and fruit defor-mations. In late summer and fall, most of thedamage consists of marking and puncturing ofmature fruit. The following feeding damage wasobserved:

Terminal and lateral tips – varying degrees ofstunting and growth deformations such as lossof side shoots, swelling of internodes, exces-sive foliar growth and formation of multipleweak leaders.

Flower buds – feeding on or near the pepperflower bud can cause loss of a flower bud,excessive stunting of the flower stem, andabnormal growth of flower buds or fruit.

Fruit – feeding on small developing fruit cancause deformation of the blossom end whilefeeding on fruit walls causes punctures anddiscolouration of the fruit surface. See colourphoto 30.


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Economic ImportanceDamage caused by lygus feeding on the termi-nal and lateral tips becomes evident only weeksafter the feeding injury. At that point thegrowth and production of the injured plant istypically compromised, regardless of correctivepruning. Yield losses from lygus feeding canrange from the loss of one to several fruit setsper plant, depending on severity of the feedingdamage. During late summer, high populations(>1 bug /20 plants) feeding on pepper fruit cansignificantly reduce total and marketable yield.

MonitoringLygus bugs are very alert and hide or dispersewhen disturbed. Such behavior hinders accu-rate estimations of lygus densities. Theirpresence may be detected by positioning yellowor white sticky traps approximately 15 cmabove the pepper canopy. Also, learn to recog-nize feeding symptoms on plants. The eco-nomic impact of lygus infestations can bedetermined by comparing feeding damage ininfested and lygus-free areas. During spring andearly summer, estimate fruit set per plant whileduring fall, estimate percentage of culled fruitwith lygus damage.

Cultural ControlWeeds around the greenhouse encourage thebuildup of lygus populations. Frequent mowingor weed control throughout the season canreduce the size of lygus populations. Mowing orweed-killing weedy patches only once or twiceduring the season disturbs lygus populationsand could result in greenhouse invasions.

Pruning strategy: In the presence of lygus,reduce pruning cycle to create more feedingsites and provide alternate shoots that may beneeded to replace damaged heads.

Biological ControlThere are currently no effective methods availablefor biocontrol of lygus bugs on indoor crops.

Chemical Control

Action threshold:

Accept low percentage of damage when lyguspopulations are stable (adults only). Applycontrol measures when low percentage ofdamage coincides with presence of both lygusnymphs and adults.

Thiodan 4E (endosulfan)

Use 1.25 - 1.5 mL / L water. Thorough cover-age of undersides of leaves is essential. Do notapply more than twice per season. Thiodaneffectively controls both adult and nymphalstages. However, it affects negatively themajority of established biologicals and makesgrowers dependent on chemicals for the controlof subsequent pest outbreaks. Thiodan alsohas high mammalian toxicity. Economic lossesdue to lygus feeding damage should be weighedcarefully against the cost of loss of establishedbiocontrol agents, chemical dependence for thecontrol of subsequent pest outbreaks, and thepotential losses from those outbreaks. Do not

apply within 2 days of harvest. Re-entry

period for unprotected workers is 48 hours.


Dibrom can only be used during end-of-seasoncleanup, in an empty greenhouse. Use 10mL/100m2 of greenhouse space when applyingDibrom to the heating pipes. Apply undilutedliquid to evenly spaced cold pipes. Do notallow Dibrom to drip from the pipes onto thefloor as it won’t completely volatilize on thefloor. Immediately heat the pipes to at least41°C and keep vents closed for at least 3 hoursafter the pipes are hot. Keep the greenhouseclosed over-night following application andventilate well before entering.


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Psyllids

TaxonomyPsyllids are small insects resembling aphids insize and feeding habits. The pear psylla is aserious pest of pear. In some countries, psyllidsare more numerous than aphids. In B.C. green-houses, the potato (tomato) psyllid damagesboth peppers and tomatoes. The potato psyllid,Bactericera cockerelli (synonym: Paratrioza cockerelli),

is a migratory pest from southern USA. Eachyear, adults migrate north driven by spells of hotweather. The potato psyllid is a pest of solana-ceous plants, which include tomatoes, potatoesand sweet peppers. Whether psyllids can over-winter in B.C. is still under debate. They cansurvive long periods of moderately cold tem-peratures and short periods of below freezingtemperatures (-2 to -5oC).

Appearance and Life CycleAdult psyllids are about 2.5 mm long and haveclear wings that rest roof-like over the body. Onemergence, adults are light yellow to pale greenand turn grey-black within five days. They havea characteristic white stripe on the first and thelast abdominal segment. The eggs are small, 0.3mm long, and are supported by a short stalkattached to the leaf. On peppers, eggs are laid onthe young leaves. Psyllids pass through fivenymphal stages. Nymphs resemble whiteflyscales, but are larger in the last two stages. Allnymphal stages have a fringe of short spinesaround the edge of scales. Unlike whiteflies, theymove slowly when disturbed.



Fecundity 300 eggs/female

Longevity of adult 40 days

Developmental stages Egg, 5 nymphalstages and adult

Damage on Greenhouse PeppersIn the past few years, psyllids have been foundearly in the season on pepper crops. They haveestablished and reproduced successfully through-out the growing season and in some greenhouseshave increased to outbreak levels. Infestationsof psyllids early in the growing season should becontrolled. Establishment and reproduction ofpsyllids on mature peppers is typically poor withnymphs often failing to complete their life cycle.Late infestations of psyllids are of no economicconcern.

Discolouration of leaves due to nymphal feed-ing, ‘psyllid yellows’, has not been observed onpepper crops. Both nymphs and adults producelarge quantities of honeydew, which is coatedwith a white wax and closely resembles grains ofsugar or salt. Feeding by large numbers ofnymphs can result in excessive accumulation ofhoneydew on the foliage and around the fruitcalyx. Granulated honeydew can promotegrowth of sooty mould, which can affect market-ability of the fruit.

MonitoringThe presence of sugary honeydew on pepperfoliage is usually the first sign of psyllid infestation.The presence of eggs on young pepper leaves isalso a good indicator. See colour photo 31.

Neon-green, neon-orange and standard yellowsticky traps are very attractive to both male andfemale psyllids. Sticky traps hung near the top ofthe plant canopy will capture the greatestnumber of adults. Trapping can be used toreduce, but not eliminate, the population ofadults in the greenhouse.

Cultural ControlEarly detection and removal of infested leavesor plants from the greenhouse may restrict ordelay population increase.

Biological ControlThe parasitic wasp, Tamarixia triozae, has beenfound to parasitize nymphs of the potato psyllid.It has proven to be very effective in controllingpsyllid outbreaks on greenhouse peppers and


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tomatoes. The wasp parasitizes the fourth andfifth nymphal stages. Parasitized nymphs changecolour from green to brown. The parasitic waspchews a hole in the pupal case and emergesthrough it. Development from egg to adult takesfrom 16 to 20 days, depending on temperature.

Chemical Control


Use 20 mL/L water. Insecticidal Soap acts onlyby direct contact so thorough coverage is essen-tial. Phytotoxicity can occur if the label rate isexceeded or applied in direct sunlight. Do not

apply more than twice per crop cycle or

within 3 days of harvest.


pyrethrin)

Use 50mL/L water. Insecticidal Soap acts onlyby direct contact so thorough coverage is essen-tial. Phytotoxicity can occur if the label rate isexceeded or if applied in direct sunlight. Do not

apply within 5 days of harvest.


One application of Dibrom provides an effec-tive control of all stages of psyllids.

Dibrom can only be used during end-of-seasoncleanup, in an empty greenhouse. Use 10mL/100m2 of greenhouse space when applyingDibrom to the heating pipes. Apply undilutedliquid to evenly spaced cold pipes. Do not allowDibrom to drip from the pipes onto the floor asit won’t completely volatilize on the floor.Immediately heat the pipes to at least 41°C andkeep vents closed for at least 3 hours after thepipes are hot. Keep the greenhouse closed over-night following application and ventilate wellbefore entering.

Thrips

TaxonomyThe western flower thrips, Frankliniella occidentalis

and the onion thrips, Thrips tabaci are commonlyfound on greenhouse peppers. Both species cancause economic damage to the crop. Echinothrips

americana and Thrips fuscipennis, are occasionalpests. E. americana adults are about the same sizeas the western flower thrips, but their wings havecharacteristic white basal markings. This givesadults the appearance of having a white bandacross the thorax (shoulders) when the wings arefolded. They feed, develop and pupate on theplant. Unlike the other two thrips, they feed andlay eggs in the leaf tissue rather than in and nearthe flowers. At high densities they will alsodamage the fruit. During summer they are foundin high numbers in the lower leaf canopy. Feed-ing and egg-laying causes damage to the leavesand fruit. Predators effective against westernflower and onion thrips have not been successfulagainst E.americana.

Appearance and Life Cycle of theWestern Flower and Onion ThripsThe adult western flower thrips is 1.3 mm long,elongated and yellowish with a brownish-blackabdomen (see Figure 5-4). The larva is translu-cent white to yellowish. The eggs are insertedinto the leaf tissue. At high infestations, eggs arealso inserted into developing fruit.

Thrips spend most of their life on the plant butthey pupate in the organic matter on the green-house floor. They are weak fliers but windcurrents can carry them a long distance. Theyinvade greenhouses through open vents anddoors. Cutting grass around or near a greenhousewill cause thrips to disperse. Reduce venting

Figure 5-4. Adult Western Flower Thrips.

Source: Anonymous 1952.


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temporarily during grass cutting to prevent thripsfrom entering the greenhouse.

Damage symptomsThrips can damage a plant directly by feeding orlaying eggs and indirectly by transmitting tomatospotted wilt virus (TSWV). Thrips feed on thelower leaf surface, growing terminals, on budsand on flowers. On mature pepper fruit, nymphsfeed under the calyx. Like spider mites theypuncture and kill individual cells. Feeding dam-age results in “silver” discoloured or necroticspots. The damage is often accompanied by thepresence of black frass. Eggs inserted in theplant tissue cause local discolouration anddeformity. When eggs are laid in young fruit thedamage expands and elongates slightly as thefruit grows. Fruit with feeding or egg-layingdamage is unmarketable.

MonitoringMonitoring includes weekly inspection of stickytraps and the plant canopy. Thrips are veryattracted to blue sticky traps but the yellow trapsare used more often as they can be used tomonitor other insect pests. Use a minimum of 25traps/ha, positioned 30 cm above the canopy. Ahigher number of traps per hectare can nega-tively impact Aphidius populations.

Inspect plants for foliar damage and presence ofthrips and their natural enemies. Tap flowersand count the number of thrips that disperse.

Biological Control with PredatoryInsects and MitesThrips have high fecundity and relatively shortdevelopmental times, allowing populations tobuild very rapidly. Outbreaks of thrips can causesubstantial economic damage in a short periodof time and can be difficult to control biologi-cally, particularly during winter and early spring.Preventive control is therefore the main strategywhen dealing with this pest. Effective season-end cleanup and frequent crop monitoring isessential for successful preventive control.

During winter and early spring, start releasingAmblyseius cucumeris and Hypoaspis. Predation by

A. cucumeris and Hypoaspis is restricted to the firstinstar and pupal stages only. For successfulbiological control of thrips during winter, largeintroduction rates of these predatory mites arerequired to offset their selective predationpattern. Predatory mites will provide adequatecontrol only when introduced before thrips reachdamaging levels. Starting mid-March, releaseOrius insidiosus. Orius has a diapause stage andcannot be introduced earlier. This predatory bugis very effective in controlling thrips and willalso feed on other small soft-bodied insects andmites. Use curative rates of Orius to controloutbreaks of thrips. See Table 5-6.

Chemical control

Nicotine Smoke

Use one can / 300m3, spacing the fumigatorsthroughout the greenhouse. Only one applica-tion is allowable per planting. The greenhouseshould be tightly closed and temperature main-tained at 22 – 25ºC. If a circulating fan ispresent in the greenhouse, it should be turned onfor about 15 minutes to ensure uniform distribu-tion. Ventilate the greenhouse thoroughly thenext day after fumigation. Warning: Nicotine

smoke is extremely hazardous. Use a fullfacemask with approved canister and protectiveclothing when entering a greenhouse that is stillbeing ventilated. Supplied air must be used ifthere is a risk of exposure to the smoke. Do not

use within 5 days of harvest.

Cleanup Using Dibrom (naled)

Application of Dibrom for greenhouse pepperscan only be made during end-of-season cleanupin an empty greenhouse. Use 10mL / 100m2 ofgreenhouse space when applying Dibrom to theheating pipes. Apply undiluted liquid to evenlyspaced cold pipes. Do not allow Dibrom to dripfrom the pipes onto the floor as it won’t com-pletely volatilize on the floor. Immediately heatthe pipes to at least 41°C and keep vents closedfor at least 3 hours after the pipes are hot. Keepthe greenhouse closed over-night followingapplication and ventilate well before entering.


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Tab

le 5

-6. C

om

mer

cial

ly a

vaila

ble

bio

log

ical

co

ntr

ol a

gen

ts f

or

thri

ps

Nam

e

Ap

pea

ran

ce a

nd

life

cyc

le

Co

mm

ents

Adu

lts, a

bout

0.8

mm

long

, hav

e a

pear

-sha

ped,

bei

ge-p

ink

body

and

ar

e ve

ry m

obile

. N

ymph

s ar

e sm

alle

r an

d re

sem

ble

adul

ts in

sha

pe

and

mob

ility

. E

ggs

are

tran

spar

ent w

hite

and

are

ofte

n fo

und

atta

ched

to

leaf

hai

rs o

n th

e un

ders

ide

of le

aves

. L

ife

cycl

e at

20

OC

(68

oF

) E

gg to

adu

lt 11

day

s F

ecun

dity

35 e

ggs/

fem

ale

Dev

elop

men

tal s

tage

s E

gg, l

arva

, 2 n

ymph

al s

tage

s, a

dult

Pre

daci

ous

stag

es

Nym

phs

and

adul

t

Predatory mite Amblyseius cucumeris

The

se p

reda

tors

feed

on

the

first

larv

al s

tage

of t

hrip

s. T

hey

can

also

feed

on

the

eggs

of m

any

mite

spe

cies

. A. c

ucum

eris

has

a r

elat

ivel

y lo

w

tole

ranc

e fo

r lo

w h

umid

ity. C

omm

erci

ally

ava

ilabl

e st

rain

s ha

ve r

educ

ed

tend

ency

to d

iapa

use

and

can

be u

sed

thro

ugho

ut th

e ye

ar. T

hey

are

avai

labl

e in

a b

ran

carr

ier

or in

slo

w-r

elea

se b

ags.

R

elea

se r

ates

*:

In b

ran

carr

ier:

pre

vent

ive

rele

ases

bi-w

eekl

y of

up

to 5

0 pr

edat

ors/

m2 ;

cura

tive

rele

ases

req

uire

up

to 1

00 p

reda

tors

/m2

Slo

w-r

elea

se b

ags:

1 b

ag/6

-8 p

lant

s, e

very

6-8

wee

ks (

By

the

end

of th

e cr

op, e

very

pla

nt s

houl

d ha

ve a

bag

.)

Adu

lts a

re d

ark-

brow

n, la

rger

and

mor

e ag

gres

sive

than

A. c

ucum

eris

. E

ggs

are

initi

ally

tran

spar

ent a

nd tu

rn p

artly

bro

wn

with

tim

e. T

hey

are

laid

in g

roup

s on

hai

rs o

n th

e un

ders

ide

of le

aves

. L

ife

cycl

e at

20

OC

(68

oF

) E

gg to

adu

lt N

ot a

vaila

ble

Fec

undi

ty

N

ot a

vaila

ble

Dev

elop

men

tal s

tage

s E

gg, l

arva

, 2 n

ymph

al s

tage

s, a

dult

Predatory mite Amblyseius degenerans

Pre

daci

ous

stag

es

Nym

phs

and

adul

t

The

se m

ites

feed

on

first

and

sec

ond

stag

e th

rips.

The

y do

n’t

have

di

apau

se a

nd c

an b

e us

ed th

roug

hout

the

year

. The

y to

lera

te lo

w h

umid

ity.

Pol

len

is n

eces

sary

for

esta

blis

hmen

t.

Pre

vent

ive

rele

ase

rate

*: r

elea

se o

nce,

at 1

/m2 a

fter

polle

n be

com

es

avai

labl

e.

Thi

s pr

edat

or fe

eds

on e

ggs

of th

e pr

edat

ory

mid

ge A

phid

olet

es, w

hich

re

duce

s su

bsta

ntia

lly e

ffect

iven

ess

of a

phid

s co

ntro

l by

Aph

idol

etes

. T

here

fore

, use

of t

he A

. deg

ener

ans

on p

eppe

rs is

cur

rent

ly n

ot

reco

mm

ende

d.

Adu

lts a

re d

ark

brow

n w

ith a

gra

y-w

hite

sec

tion

on th

e w

ings

. Fem

ales

ar

e sl

ight

ly la

rger

than

mal

es. N

ewly

em

erge

d ny

mph

s ar

e sh

iny

and

colo

urle

ss. T

hey

chan

ge g

radu

ally

from

yel

low

to b

row

n. E

ggs

are

very

sm

all a

nd e

mbe

dded

in th

e le

af ti

ssue

. L

ife

cycl

e at

21

OC

(70

oF

) E

gg to

adu

lt 34

day

s F

ecun

dity

13

0 eg

gs/fe

mal

e

Long

evity

3-

4 w

eeks

D

evel

opm

enta

l sta

ges

Egg

, 5 n

ymph

sta

ges,

adu

lt

Predatory bug Orius insidiosus

Pre

daci

ous

stag

es

Nym

phs

and

adul

t

Thi

s pr

edat

ory

bug

feed

s on

the

wes

tern

flow

er a

nd o

nion

thrip

s, a

s w

ell a

s on

the

eggs

of m

oths

, spi

der

mite

s an

d w

hite

flies

. All

stag

es c

an d

ispe

rse

wel

l thr

ough

out t

he p

eppe

r ca

nopy

. In

the

abse

nce

of p

rey

they

can

sur

vive

on

pol

len.

Oriu

s ha

s a

diap

ause

sta

ge a

nd c

an o

nly

be u

sed

from

Mar

ch to

S

epte

mbe

r.

Rel

ease

rat

es*:

P

reve

ntiv

e

Lo

w to

med

ium

infe

stat

ions

Med

ium

to h

igh

infe

stat

ions

0.5-

1.0/

m2 ;

1-

5/m

2 ;

1

0/m

2 ;

1-2

intr

oduc

tions

,

2

intr

oduc

tions

,

1 in

trod

uctio

n in

hot

spo

t 2

wee

ks a

part

2

wee

ks a

part

Adu

lts a

re 1

mm

long

and

ligh

t bro

wn.

Lar

vae

and

first

nym

phal

sta

ge

are

whi

te.

Lif

e cy

cle

at 2

0 OC

(68

oF

) E

gg to

adu

lt A

bout

11

days

F

ecun

dity

Not

ava

ilabl

eLo

ngev

ity

N

ot a

vaila

ble

Dev

elop

men

tal s

tage

s E

gg, l

arva

, 2 n

ymph

al s

tage

s, a

dult

Predatory mites Hypoaspis miles, and H. aculifeir

Pre

daci

ous

stag

es

Nym

phal

sta

ges

and

adul

t

The

se p

reda

tors

feed

on

thrip

s pu

pae

in th

e so

il. T

hey

do n

ot h

ave

a di

apau

se s

tage

and

can

be

used

thro

ugho

ut th

e ye

ar.

Bot

h sp

ecie

s ca

n su

rviv

e by

feed

ing

on o

ther

soi

l art

hrop

ods

or a

lgae

. The

y pr

ovid

e on

ly

part

ial c

ontr

ol a

nd s

houl

d be

use

d in

con

junc

tion

with

oth

er b

ioco

ntro

l ag

ents

. The

y lik

e m

oist

soi

l and

tem

pera

ture

s >

15 O

C.

Rel

ease

rat

es (

one

intr

oduc

tion

only

)*:

Pre

vent

ive

Lo

w to

med

ium

infe

stat

ions

M

ediu

m to

hig

h in

fest

atio

ns

100

/m2

20

0/m

2

50

0/m

2

*- R

elea

se r

ates

pre

sent

ed in

the

tabl

e ar

e fo

r ge

nera

l gui

danc

e on

ly. T

hey

shou

ld b

e ad

just

ed a

ccor

ding

to th

e le

vel o

f pes

t inf

esta

tion

and

exis

ting

po

pula

tions

of p

reda

tors

. For

furt

her

info

rmat

ion

refe

r to

the

tech

nica

l man

uals

pro

vide

d by

the

bio-

cont

rol p

rodu

cers

.


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Two-spotted Spider Mite

TaxonomyThe two-spotted spider mite, Tetranychus urticae

and closely related carmine mite, Tetranychus

cinnabarinus can be found on greenhouse pep-pers. For both mites, feeding damage on pepperand control strategies are the same, thereforeonly spider mites may be referred to in thisdocument. Spider mites feed on more than 900plant species including some of the commongreenhouse weeds like chickweed, cress, andoxalis. Mites and their close relatives, thespiders, are not classified as insects. They differin several ways, including lack of antennae andadults usually with eight legs instead of six.Due to their small size however, magnificationwould be required to observe these differences.

Appearance and Life CycleAdults are about 0.5 mm in length. Spring andsummer generations of the two-spotted spidermite are typically light green in colour with twodark spots on the back. The adult female of thecarmine mite is dark plum-coloured. Eggs areround, small (~0.1mm) and pearly white incolor. They can be found on the underside ofthe leaf and can be viewed with a hand lensmagnifying 10 times. Spider mites pass throughthe one larval and two nymphal stages beforebecoming adult. All stages feed on plant tissue.See colour photos 32 & 33.

Life cycle at 20°C (68°)


Fecundity 80 eggs perfemale


Population distribution 65% eggs*; 35%adults andnymphs

(*Eggs can survive applications of mostmiticides, therefore effective chemical controlrequires two applications, 5 to 7 days apart.)

Diapause

Spider mites diapause as mated females.Diapause is a non-feeding state without repro-duction induced by short day-length,unfavorable food supply, and low temperature.In B.C., diapause occurs from September toMarch. Both species are deep orange-red indiapause. They over-winter in soil, insulationand small cracks in the greenhouse.

Dispersal of Spider MitesSpider mites disperse from the pepper plant inresponse to the increase in their own numbers;the higher the density the more mites willdisperse. Methods of dispersal include: hori-zontal, plant-to-plant dispersal; vertical, up thecanopy and via supporting trellises; and aerial,ballooning and ‘passive flight’.

Typical summer conditions with high tempera-tures, low RH and extensive ventilation, allowsmites that moved to the top of the canopy andhorizontal wires to drift on air currents. Thisform of dispersal contributes to (1) the expan-sion of existing hot spots and (2) formation ofnew ones, especially at the top of the canopy.Summer monitoring strategies should considerthe extent of aerial dispersal and mite distribu-tion within the canopy. Early application ofcontrol measures, removal of heavily infestedleafs or plants, or spot spraying with water or amiticide will reduce spider mite populationsand consequently their dispersal.

MonitoringAssessment of spider mite infestations relies onthe examination of the undersides of leaves fortheir presence, and searching for the signs oftheir feeding damage. In the absence of spidermite infestations inspect leaves randomlythroughout the canopy. In the presence ofminor damage, inspect leaves at and above thedamaged area. In the presence of severe dam-age, focus on leaves at the top of the canopy inhotspots and surrounding areas.

Although spider mites disperse by other meth-ods, during late spring and summer they candrift on air currents, causing new infestations toappear at the top of the pepper canopy. During


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this period the monitoring schedule shouldinclude examination of the upper canopy.

Damage Symptoms and EconomicImportanceSpider mites feed on the underside of leaves,piercing and sucking the content of leaf cells.The leaves develop a chlorotic and fleckedappearance. Mite feeding causes closure ofplant stomata, resulting in decreased CO

2

uptake, transpiration and photosynthesis. Thisultimately leads to a reduction in yield.

Control Strategies

Biological Control with PhytoseiuluspersimilisThe biology and behavior of the two-spottedspider mite and its predator P. persimilis areaffected by changes in temperature. Seasonaltemperature fluctuations affect all aspects ofmonitoring, choice of predator and release rates.

In south coastal B.C., greenhouse peppers aregrown in a relatively narrow range of ADT, from19.0oC in the winter or early spring to 23.5oC inthe summer. In the Southern Interior, averagesummer temperatures can reach up to 25oC.The two extremes,19oC and 25oC, are used hereto illustrate the effect of temperature on spidermite development and the effectiveness of it’sbiological control with P. persimilis. Populationtrends were derived with the use of predictivemodels. At 25oC, spider mites developfaster, form more generations andhave a greater population increasethan at 19oC (see Figure 5-5).

During summer, populations ofspider mites started with the samenumber of females, will reach higherlevels and cause more damage togreenhouse peppers than during thewinter or spring. Spider mitepopulations should be monitoredfrequently during summer to detectearly infestations and prevent rapidpest outbreaks. Early detection andearly releases of predators will im-prove the success rate and signifi-

cantly reduce costs of biological control.

Populations of P. persimilis increase faster thanspider mite populations within the 18 to 27oCtemperature range. Within this range, biologicalcontrol of spider mites with P. persimilis is veryeffective. Outside of this temperature range,population growth of the predatory mite isslower than spider mites. This makes biologicalcontrol less effective. Climate conditions in BCgenerally favour optimal performance of thispredator.

Effect of Temperature and ReleaseRates on Biological ControlAt both release rates, populations of spidermites would reach higher levels at 25oC than19oC, before being controlled by P. persimilis (seeFigure 5-6 A and B). Reaching high infestationlevels just before P. persimilis controls spidermites often happens in the summer and shouldnot be considered as an indication of ineffectivebiological control. At both temperatures,populations of spider mites would increase lessat the higher release rate of P. persimilis, i.e. atthe ratio 1:20 rather than 1:28.

The intensity of spider mite outbreaks and theeffectiveness of their control depend on green-house temperatures and release rates of P.

persimilis. Greenhouse temperatures cannot bechanged for the benefit of biological controlbut release rates can be adjusted to offset

Figure 5-5. Differences in spider mite population growth at 19oC

and 25oC.The two populations started with one female mite.

0

5000

10000

15000

20000

25000

30000

35000

40000

45000

0 1 2 3 4 5 6 7

Weeks

Sp

ider

mite

s (im

mat

ure

s an

d a

du

lts)

Devlopment at 19 C

Development at 25 C

Development at 19o C

Development at 25o C


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increasing temperatures. At high temperaturesmore predators should be released and theyshould be released as soon as possible.

Although it is very useful to have release ratesof P. persimilis based on area (see Table 5-7),they should be treated as a guide only. Releaserates of P. persimilis should be adjusted accord-ing to pest density, i.e. the higher the pestdensity the more predators should be released.Spider mite populations are controlled veryrapidly when predator-to-prey ratios are 1:10and 1:20. Release rates should ensure this ratiois reached within a reasonable time (2-3weeks). When release rates are too low, it willtake longer for biological control to take effectand in the mean-time mites may reach damag-ing levels.

Alternatively release rates can be adjusted byreducing populations of spider mites beforeintroduction of P. persimilis. De-leafing orremoval of heavily-infested plants and spotspraying a selected number of plants with wateror a miticide are just a few methods for improv-ing the predator to prey ratio.

Frequency of ReleasesFrequency of P. persimilis releases depends on thelevel and distribution of spider mites within theinfested area. In a hot spot, less frequent butlarger introductions are recommended. This

release strategy prevents spider mite populationsfrom reaching high levels. Releases should bediscontinued when predators become well estab-lished and have produced numerous offspring.

Outside the hot spot area, where spider mitesare at low levels, releases should continueweekly at a low release rate, until control isachieved.

The Pest-in-First MethodThis strategy is used typically during earlyspring and attempts to establish the pest eitherin patches or evenly throughout the green-house. Predators are then added to cycle andmaintain low spider mite populations over time.Inoculating plants with P. persimilis on spidermite infested leaves is a similar strategy.

Measuring Effectiveness of BiologicalControl of Spider Mites.Biological control is effective when:

• Many predators of spider mites are found inthe infestation area.

• Spider mite levels are decreasing and leavesabove the infestation do not have feedingdamage.

Figure 5-6. Effectiveness of biological control of spider mites with P. persimilis released at two

predator to prey ratios (a) 1:20 and (b) 1:28 and two temperatures; 19oC and 25oC.

Each population started with two females.

0

300

600

900

1200

1500

0 1 2 3 4 5 6 7 8

Weeks

Sp

ider

mite

s (im

mat

ure

s an

d a

du

lts)

Bio-control at 19 C

Bio-control at 25 C

P.persimilis Predator/prey

ratio 1:20

0

300

600

900

1200

1500

0 1 2 3 4 5 6 7 8

Weeks

Sp

ider

mite

s (im

mat

ure

s an

d a

du

lts)

Bio-control at 19 C

Bio-control at 25 C

P.persimilis Predator/prey

ratio 1:28

BA o

o

o

o


5.

Pest

an

d D

isease M

an

ag

em

en

t

Commercially Available Bio-ControlAgentsSeveral predators can feed on spider mites andcontribute to their control. In addition to thethree main predators (see Table 5-8) theyinclude Amblyseius cucumeris, Amblyseius

Season Monitoring Control Strategies W

inte

r (D

ecem

ber

- Ja

nu

ary)

Monitor biweekly in the absence of spider mites, and otherwise weekly. Pay specific attention to areas that are known to over-winter spider mites. Look for mites and feeding damage throughout the canopy.

During this period biological control of spider mites relies entirely on Phytoseiulus persimilis. Apply P. persimilis before appearance of spider mites in areas that typically host over-wintering mites. Release predators at the first sign of spider mite infestations. Use high rates, and few concentrated releases in hot-spots, and low rates with weekly releases around hot-spots.

Sp

rin

g

(Feb

ruar

y –A

pri

l)

Monitoring spider mites as in winter. In addition, assess the effectiveness of ongoing biological control and start monitoring Stethorus and Feltiella.

Rely on P. persimilis for control of spider mites, but start inoculating the crop with Stethorus and N. fallacis in February, and with Feltiella in mid-March. Release these predators in areas with spider mites. Once established, they will disperse throughout the greenhouse and greatly contribute to the control of spider mites throughout the summer. Release P. persimilis in and around spider mite hot-spots, and adjust introduction rates and frequency of releases to the level of spider mite infestations.

Su

mm

er

(May

-Au

gu

st)

Monitor weekly and pay close attention to the areas that had spider mite infestations in the last few weeks. They tend to reappear. Include monitoring of the upper canopy to address aerial dispersal of spider mites. Monitor for Stethorus and Feltiella and assess effectiveness of biological or chemical control.

During summer increase reliance on Feltiella and Stethorus for the control of new spider mites infestations. Use P. persimilis along with Feltiella to control expanding hot-spot areas. When starting biological control of a hot spot with medium pest infestation, consider reducing spider mite populations before predator releases. Remove heavily infested plants, deleaf, or spray selected plants with water or miticide. This will reduce the time required for biological control to become effective and minimize mite damage to the crop. Introduction of predators into heavy infestations will stand no chance of successful control. Timely application of chemical control will reduce crop damage and dispersal of spider mites throughout the greenhouse.

Fal

l (S

epte

mb

er –

N

ove

mb

er)

Monitor biweekly when predators of spider mites are numerous or weekly in the presence of spider mite infestations.

As in the winter and early spring biological control of spider mites in the fall relies entirely on P. persimilis. Release P. persimilis in and around spider mite hot-spots and adjust introduction rates and frequency of releases to the level of spider mite infestations. Presence of spider mite infestations during fall can warrant application of a miticide throughout the greenhouse to prevent the mites from over-wintering.

Release rates and release frequency of P. persimilis Apply P. persimilis in and around hot-spots at different rates and release frequencies. In the hot-spot area, release high rates (>20 predators/plant) in a few, concentrated releases. Increase release rates with increasing spider mite levels. In the area surrounding the hot-spot, release low rates weekly.

degenerans, Orius spp, lacewing species, Dicyphus

hesperus, and others. They cannot, however,control spider mite populations on their own.

Table 5-7. Summary of seasonal monitoring and biological control strategies for thetwo-spotted spider mite.


5.

Pest

an

d D

isease M

an

ag

em

en

t

Tab

le 5

-8. C

om

mer

cial

ly a

vaila

ble

bio

log

ical

co

ntr

ol a

gen

ts f

or

the

two

-sp

ott

ed s

pid

er m

ite.

Name

Ap

pea

ran

ce a

nd

life

cyc

le

Ap

plic

atio

ns

Adu

lts a

re p

ear-

shap

ed, s

light

ly la

rger

in s

ize

than

spi

der

mite

s an

d lig

ht

red

in c

olou

r. N

ymph

s ar

e tr

ansp

aren

t off-

whi

te in

col

our.

The

y m

ove

fast

er th

an s

pide

r m

ites.

The

egg

is o

val a

nd a

lmos

t tw

ice

as b

ig a

s th

e eg

g of

the

spid

er m

ite. S

ee c

olou

r ph

oto

34.

Lif

e cy

cle

at 2

0 OC

(68

oF

) E

gg to

adu

lt 7.

5 da

ys

Fec

undi

ty

4

eggs

/fem

ale/

day

Long

evity

14

– 4

0 da

ys

Dev

elop

men

tal s

tage

s E

gg, l

arva

, nym

phs

and

adul

t

Predatory mite Phytoseiulus persimilis

Pre

daci

ous

stag

es

Nym

phs

and

adul

ts.

P. p

ersi

mili

s is

a v

ery

effe

ctiv

e pr

edat

or th

at in

crea

ses

repr

oduc

tive

capa

city

in r

espo

nse

to th

e pr

ey s

uppl

y. I

t doe

sn't

diap

ause

and

its

use

depe

nds

on c

ontin

ued

war

m c

ondi

tions

. Thi

s pr

edat

or d

ispe

rses

or

star

ves

to d

eath

afte

r re

duci

ng a

mite

pop

ulat

ion

to b

elow

det

ecta

ble

leve

ls. T

his

can

caus

e re

curr

ent s

pide

r m

ite o

utbr

eaks

and

lim

its p

reve

ntiv

e us

e of

this

pr

edat

or. P

reve

ntiv

e ap

plic

atio

ns c

an, h

owev

er, b

e us

ed in

the

win

ter

or

early

spr

ing

befo

re a

ppea

ranc

e of

spi

der

mite

s in

are

as th

at ty

pica

lly h

ave

over

-win

terin

g m

ites

or a

roun

d th

e ho

t-sp

ots

area

s th

roug

hout

the

seas

on.

Rel

ease

rat

es (

pred

ator

s/m

2 )*:

Pre

vent

ive

L

ow to

med

ium

infe

stat

ions

M

ediu

m to

hig

h in

fest

atio

ns

1- 3

1

0

20

-50

A

dults

are

abo

ut 2

mm

long

and

pin

k–br

own

in c

olou

r. T

he la

rvae

are

cr

eam

y-ye

llow

with

som

e br

own

colo

urat

ion.

The

pup

ae a

re fo

und

insi

de

the

whi

te c

ocoo

ns th

at a

re d

epos

ited

alon

g th

e ve

ins

of th

e le

aves

. S

ee c

olou

r ph

otos

35

& 3

6.

Lif

e cy

cle

at 2

0 OC

(68

oF

) E

gg to

adu

lt 10

-15

days

S

ex r

atio

60

–70

% fe

mal

es

Fec

undi

ty

12 –

20 e

ggs/

fem

ale

Long

evity

4-

6da

ys

D

evel

opm

enta

l sta

ges

Egg

, 4 la

rval

sta

ges,

pup

a, a

dult

P redatory midgeFeltiella acarisuga

Pre

daci

ous

stag

es

Onl

y la

rval

sta

ges

An

effe

ctiv

e pr

edat

or w

ith g

ood

disp

ersa

l and

hos

t-fin

ding

abi

lity;

onc

e es

tabl

ishe

d ca

n co

ntro

l and

pre

vent

out

brea

ks o

f spi

der

mite

pop

ulat

ions

. P

rese

nce

of c

ocoo

ns a

long

vei

ns o

n lo

wer

-leaf

sur

face

s is

indi

catio

n of

the

pred

ator

est

ablis

hmen

t. T

here

is n

o ev

iden

ce fo

r ph

otop

erio

d-in

duce

d di

apau

se in

the

BC

str

ain,

but

feed

ing

on d

iapa

usin

g T

. urt

icae

see

ms

to

indu

ce d

iapa

use,

whi

ch li

mits

use

of t

his

pred

ator

dur

ing

win

ter,

ear

ly

sprin

g an

d fa

ll. T

his

pred

ator

req

uire

s th

e pr

esen

ce o

f ade

quat

e pr

ey fo

r su

cces

sful

est

ablis

hmen

t. R

elea

se r

ates

(pu

pae/

ha)*

: P

reve

ntiv

e

Low

to m

ediu

m in

fest

atio

ns

Med

ium

to h

igh

infe

stat

ions

no

t rec

omm

ende

d

600

to 1

200

up

to 2

500

Adu

lt be

etle

s ar

e ro

und,

2 m

m lo

ng a

nd s

hiny

bla

ck. T

he la

rvae

are

dar

k br

own

and

dens

ely

cove

red

with

hai

r. P

upae

are

foun

d on

the

low

er le

af

surf

ace

and

alon

g th

e ve

ins

of th

e le

aves

. See

col

our

phot

os 3

7 &

38.

L

ife

cycl

e at

21

OC

(70

oF

) E

gg to

adu

lt 23

day

s F

ecun

dity

750-

1000

egg

s/fe

mal

eLo

ngev

ity

400-

700

days

Dev

elop

men

tal s

tage

s E

gg, 3

larv

al s

tage

s, p

upa,

adu

lt

Mite Destroyer Stethorus punctillum

Pre

daci

ous

stag

es

Larv

al s

tage

s an

d ad

ult

A v

ery

effe

ctiv

e co

ntro

l age

nt w

ith g

ood

disp

ersa

l and

hos

t-fin

ding

abi

lity.

E

stab

lishm

ent o

n pe

pper

can

be

dete

rmin

ed b

y pr

edat

or p

rese

nce

or b

y th

e pr

esen

ce o

f pup

al c

ases

foun

d on

the

low

er le

af s

urfa

ce. T

his

beet

le

has

a re

prod

uctiv

e di

apau

se, b

ut c

an b

e in

trod

uced

on

the

pepp

er c

rop

as

early

as

Feb

ruar

y. It

can

est

ablis

h at

low

mite

pop

ulat

ions

. R

elea

se r

ates

*:

Pre

vent

ive

Low

to m

ediu

m in

fest

atio

ns

M

ediu

m to

hig

h in

fest

atio

ns

not

advi

sed

100

- 2

00 p

er h

ot s

pot

1

00-2

00 p

er h

ot-s

pot*

* **

The

hig

h co

st o

f thi

s pr

edat

or c

alls

for

pred

omin

antly

inoc

ulat

ive

rele

ases

.


5.

Pest

an

d D

isease M

an

ag

em

en

t

Tab

le 5

-8. (

Co

nti

nu

ed)

Co

mm

erci

ally

ava

ilab

le b

iolo

gic

al c

on

tro

l ag

ents

fo

r th

e tw

o-s

po

tted

sp

ider

mit

e.

Adu

lts a

re s

light

ly la

rger

than

adu

lt sp

ider

mite

s an

d pe

ar s

hape

d. B

oth

adul

ts a

nd n

ymph

s ar

e tr

ansp

aren

t, cr

eam

-whi

te in

col

our.

The

y m

ove

fast

er th

an s

pide

r m

ites.

Egg

s ar

e ov

al a

nd c

ream

-whi

te in

col

our.

Li

fe c

ycle

at 2

0 OC

(68

o F)

Egg

to a

dult

9 da

ys

Fec

undi

ty

23-3

0 eg

gs/fe

mal

e Lo

ngev

ity

25da

ys

D

evel

opm

enta

l sta

ges

Egg

, lar

va, t

wo

nym

phs,

adu

lt

Predatory mite Neoseiulus (Amblyseius)

californicus

Pre

daci

ous

stag

es

Nym

phs

and

adul

ts

Thi

s pr

edat

or is

mor

e to

lera

nt o

f hig

h te

mpe

ratu

res

and

low

rel

ativ

e hu

mid

ity th

an P

. per

sim

ilis.

It h

as g

ood

disp

ersa

l and

hos

t-fin

ding

abi

lity

and

can

surv

ive

with

out p

rey

if po

llen

is p

rese

nt. A

t low

spi

der

mite

in

fest

atio

ns, N

. cal

iforn

icus

can

adv

erse

ly a

ffect

the

popu

latio

n gr

owth

of

P.p

ersi

mili

s. W

hen

food

is s

carc

e, N

. cal

iforn

icus

can

pre

y on

P.p

ersi

mili

s im

mat

ures

.

Rel

ease

rat

es (

mite

s/m

2 )*:

Pre

vent

ive

L

ow to

med

ium

infe

stat

ions

M

ediu

m to

hig

h in

fest

atio

ns

0.5

-1

3- 5

u

p to

5

Adu

lts a

re s

light

ly la

rger

than

adu

lt sp

ider

mite

s an

d pe

ar s

hape

d. B

oth

adul

ts a

nd n

ymph

s ar

e tr

ansp

aren

t, cr

eam

-whi

te in

col

our.

The

y m

ove

fast

er th

an s

pide

r m

ites.

The

egg

is o

val a

nd c

ream

-whi

te in

col

our.

See

co

lour

pho

to 3

9.

Live

cyc

le a

t 20

OC

(68

o F)

Egg

to a

dult

9 da

ys

Fec

undi

ty

26-6

0 eg

gs/fe

mal

e Lo

ngev

ity

14-6

2da

ys

D

evel

opm

enta

l sta

ges

Egg

, lar

va, 2

nym

phs

and

adul

t

P redatory miteNeoseiulus (Amblyseius)

fallacis

Pre

daci

ous

stag

es

Nym

phs

and

adul

t

Goo

d di

sper

sal a

nd h

ost-

findi

ng a

bilit

y; c

an s

urvi

ve a

t low

mite

in

fest

atio

ns.

Thi

s pr

edat

or is

less

effe

ctiv

e th

an P

. per

sim

ilis

at h

igh

mite

pop

ulat

ions

. It

has

repr

oduc

tive

diap

ause

, so

it ca

n be

intr

oduc

ed fr

om M

arch

to A

ugus

t. R

elea

se r

ates

(m

ites/

m2 )*

: P

reve

ntiv

e

Low

to m

ediu

m in

fest

atio

ns

M

ediu

m to

hig

h in

fest

atio

ns

0.5

0.

5

0.

5 pl

us P

. per

sim

ilis

* R

elea

ses

rate

s pr

esen

ted

in th

e ta

ble

are

for

gene

ral g

uida

nce

only

. The

y sh

ould

be

adju

sted

acc

ordi

ng to

the

leve

l of p

est i

nfes

tatio

n an

d ex

istin

g po

pula

tions

of

pred

ator

s. F

or fu

rthe

r in

form

atio

n re

fer

to th

e te

chni

cal m

anua

ls p

rovi

ded

by th

e bi

o-co

ntro

l pro

duce

rs.


5.

Pest

an

d D

isease M

an

ag

em

en

t

Chemical ControlBefore using pesticides for control of mites orother pests, read the cautions on page 78 and onthe label. For more information on any of thechemicals, see page 147.

Avid 1.9 E (abamectin)

Use 30mL/100L of water (600 – 1,200 mL Avid1.9 in 2,000 – 4,000 L water/ha). Make no morethan 5 applications per crop. Application islimited to between February and October and/orwhen daily light intensity in the greenhouse ishigher than 700 joules/cm2 /day. This product isbest used for hot-spot treatments as it can disruptbiocontrols. Do not apply within 3 days of

harvest.

Dyno-mite / Sanmite (pyridaben)

Use 284g/1,000L water/ha. For resistance man-agement, it is not recommended to use Dyno-mitein successive applications in the same greenhouse.Rotate with at least one other product (e.g. Avid)before another application of Dyno-mite is used.Do not apply more than 2 applications per cropcycle. Do not apply within 3 days of harvest.


Use 20 mL/L of water. Insecticidal Soap actsonly by direct contact so thorough coverage isessential. Phytotoxicity can occur if the label rateis exceeded or if applied in direct sunlight. Usehigh pressure and very fine droplet size. Do not




pyrethrin)

Use 50mL/L of water). Insecticidal Soap actsonly by direct contact so thorough coverage isessential. Phytotoxicity can occur if the label rateis exceeded or if applied in direct sunlight. Do not


Cleanup Management in the FallGood control of spider mites by late August willreduce the number of spider mites diapausing inthe greenhouse. Poor spider mite control by lateAugust justifies end-of-season cleanup.

Power-wash the greenhouse inside walls. Applydormant oil on the concrete foundation andconstruction bases and on exposed soil. This willsuffocate diapausing mites and significantlyreduce over-wintering mite populations in thegreenhouse.

Dibrom (naled)

Dibrom can only be used during end-of-seasoncleanup, in an empty greenhouse. Use 10mL/100m2 of greenhouse space when applying Dibromto the heating pipes. Apply undiluted liquid toevenly spaced cold pipes. Do not allow Dibrom todrip from the pipes onto the floor as it won’tcompletely volatilize on the floor. Immediately heatthe pipes to at least 41°C and keep vents closed forat least 3 hours after the pipes are hot. Keep thegreenhouse closed over-night following applicationand ventilate well before entering.

Whitefly

TaxonomyWhiteflies are members of the insect order Hemi-ptera which also includes the aphids, psyllids andlygus bugs. The greenhouse whitefly, Trialeurodes

vaporariorum, and the sweet potato whitefly,Bemisia tabaci, are occasional pests in pepper crops.

Appearance and Life CycleAdult whiteflies have a 2mm long yellowish bodywith a mealy white wax covering on the wings.See colour photo 40. The eggs are white toyellow when laid and darken before hatching. Thenymphs are semi-transparent, oval, flattenedscales. Both adults and scales are found on theundersides of leaves.



Fecundity 150 eggs/female


Developmental stages Egg, 4 nymphs,pupa and adult


5.

Pest

an

d D

isease M

an

ag

em

en

t

Damage SymptomsAll whitefly stages have piercing-sucking mouthparts that feed on the phloem tissue. In highnumbers, feeding may cause stunted plantgrowth. Whiteflies, like aphids, secrete honey-dew. Large deposits of honeydew promote thedevelopment of sooty mould on the foliage andfruit. The sooty mould reduces yield and market-ability of the fruit.

MonitoringYellow sticky traps are the most efficient methodfor monitoring whiteflies. Use a minimum 10traps per ha positioned 30 cm above the canopy.Inspect the heads for the presence of adultwhiteflies.

Biological ControlWhitefly infestations occur only occasionally ingreenhouse peppers and preventive control is notrequired. Curative releases of Encarsia formosa

and Eretmocerus spp. can effectively control smalloutbreaks. Delphastus pusillus can be used inconjunction with the parasitic wasps to controllarger outbreaks (see Table 5-9).

Chemical Control


Use 20 mL/L water. Insecticidal Soap acts onlyby direct contact so thorough coverage is essen-tial. Phytotoxicity can occur if the label rate isexceeded or if applied in direct sunlight. Do not




pyrethrin)

Use 50mLl/L water. Insecticidal Soap acts onlyby direct contact so thorough coverage is essen-tial. Phytotoxicity can occur if the label rate isexceeded or if applied in direct sunlight. Do not



Dibrom can only be used for control of whiteflyduring end-of-season cleanup, in an emptygreenhouse. Use 10mL/100m2 of greenhousespace when applying Dibrom to the heating

pipes. Apply undiluted liquid to evenly spacedcold pipes. Do not allow Dibrom to drip fromthe pipes onto the floor as it won’t completelyvolatilize on the floor. Immediately heat thepipes to at least 41°C and keep vents closed forat least 3 hours after the pipes are hot. Keep thegreenhouse closed over-night following applica-tion and ventilate well before entering.

Miscellaneous Pests

Pepper Weevil, Anthonomus eugenii, is a seriouspest of sweet peppers in Mexico and the south-ern U.S. As the weevils feed inside fruit, theyare frequently introduced to Canada in im-ported sweet peppers. A Fraser Valley green-house pepper crop became infested in 1992.Eradication efforts were successful and therehave been no further reports of greenhouseinfestations in B.C.

Female weevils lay eggs on flower buds andfruit. After hatching, the grubs burrow into thefruit and feed on the fruit wall and seed cluster.After 8 or 9 days of feeding and 3 days pupa-tion, the adult emerges and chews a 2mm exithole in the fruit wall, usually near the top ornear the bottom of the fruit. The adults fly ashort distance, mate and start feeding on an-other plant. After a few days, the female layseggs and the cycle starts again. The life cyclecan be repeated every 2-3 weeks.

Pepper growers should be on the lookout forsymptoms as follows: 1) egg laying ‘dimple’ onthe fruit skin; 2) infested fruit may turn lightgreen with brown shoulders; 3) excessive fruitdrop; 4) 2mm exit holes; 5) adults feeding onleaves cause 3-5mm holes; 6) inside of infestedfruit has brown walls and black seeds. Seecolour photos 59 & 60.

Several other insects and mites can be poten-tial pests on greenhouse peppers. For moreinformation see Dr. D. Gillespie’s paper titled“Potential arthropod pests of greenhouse vegeta-ble crops in B.C.” on the website of Agriculture& Agri-Food Canada: http://res2.agr.ca/parc-crapac/english/3electronic_publications/e_pubs.htm


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Tab

le 5

-9. C

om

mer

cial

ly a

vaila

ble

bio

log

ical

co

ntr

ol a

gen

ts f

or

wh

itef

ly

Nam

e A

pp

eara

nce

an

d li

fe c

ycle

C

om

men

ts

Adu

lts a

re a

bout

0.6

mm

with

a b

lack

hea

d an

d th

orax

, and

a

yello

w a

bdom

en. W

hite

fly s

cale

s tu

rn b

lack

app

roxi

mat

ely

7 da

ys

afte

r pa

rasi

tism

. Li

fe c

ycle

at 2

0 OC

(68

o F)

Egg

to a

dult

28 d

ays

Fec

undi

ty

Abo

ut 3

00 e

ggs/

fem

ale

Long

evity

of a

dult

28-4

7 da

ys

Parasitoid wasp Encarsia formosa

Sex

rat

io

98-9

9% fe

mal

es

The

se w

asps

lay

eggs

in th

e th

ird a

nd fo

urth

larv

al s

tage

s of

the

gree

nhou

se

whi

tefly

sca

le.

As

a re

sult

the

pest

is k

illed

and

the

para

sitic

was

p w

ill e

mer

ge

from

the

scal

e. E

ffect

iven

ess

of th

is p

aras

itoid

dec

reas

es a

t tem

pera

ture

s be

low

18

o C a

nd d

urin

g pe

riods

of d

ull w

eath

er.

Rel

ease

rat

es*:

P

reve

ntiv

e

L

ow to

med

ium

infe

stat

ions

M

ediu

m to

hig

h in

fest

atio

ns

N/A

3-5

/m2

5-10

/m2

Min

imum

of 5

wee

kly

intr

oduc

tions

as

cura

tive.

A

dult

fem

ales

are

lem

on-y

ello

w a

nd m

ales

are

bro

wni

sh-y

ello

w

with

thic

k an

tenn

ae. W

hite

fly s

cale

s tu

rn g

olde

n ap

prox

imat

ely

7 da

ys a

fter

para

sitis

m. Li

fe c

ycle

at 2

5 OC

(77

o F)

Egg

to a

dult

20

day

s

Fec

undi

ty

50-1

00 e

ggs/

fem

ale

Lo

ngev

ity o

f adu

lt

28 d

ays

P arasitoid waspEretmocerus

eremicus

Sex

rat

io

50%

fem

ales

Like

E. f

orm

osa

this

was

p pa

rasi

tizes

third

and

four

th la

rval

sta

ges

of th

e gr

eenh

ouse

whi

tefly

and

will

als

o ki

ll sc

ales

by

feed

ing

on th

em. I

t app

ears

less

su

scep

tible

to p

estic

ides

than

E. f

orm

osa.

The

tem

pera

ture

mus

t be

abov

e 20

o C

for

it to

be

effe

ctiv

e.

Rel

ease

rat

es*:

P

reve

ntiv

e

L

ow to

med

ium

infe

stat

ions

Med

ium

to h

igh

infe

stat

ions

N/A

1-3

/m2

5-10

/m2

A

dults

are

sm

all,

1.3

– 1.

4 m

m lo

ng, s

hiny

bla

ck b

eetle

s. L

arva

e ar

e cr

eam

col

oure

d , w

ith le

gs, a

nd a

re d

istin

ctly

hai

ry. S

ee c

olou

r ph

oto

41.

Life

cyc

le a

t 25

OC

(77

o F)

Egg

to a

dult

21

day

s F

ecun

dity

150-

250

fem

ale

Long

evity

of a

dult

65 d

ays

Dev

elop

men

tal s

tage

s E

gg, l

arva

e, p

upa

and

adul

t

Predatory beetle Delphastus pusillus

Pre

daci

ous

stag

es

Larv

ae a

nd a

dults

Thi

s pr

edat

or is

ver

y ef

fect

ive

in c

ontr

ollin

g w

hite

fly b

ut r

equi

res

high

num

ber

of

whi

tefli

es fo

r its

ow

n eg

g pr

oduc

tion.

R

elea

se r

ates

*:

Pre

vent

ive

Lo

w to

med

ium

infe

stat

ions

M

ediu

m to

hig

h in

fest

atio

ns

N/A

N

/A

up

to 2

00 b

eetle

s pe

r ho

t-sp

ot

* R

elea

se r

ates

pre

sent

ed in

the

tabl

e ar

e fo

r ge

nera

l gui

danc

e on

ly. T

hey

shou

ld b

e ad

just

ed a

ccor

ding

to th

e le

vel o

f pes

t inf

esta

tion

and

exis

ting

popu

latio

ns o

f pre

dato

rs. F

or fu

rthe

r in

form

atio

n re

fer

to th

e te

chni

cal m

anua

ls p

rovi

ded

by th

e bi

o-co

ntro

l pro

duce

rs.


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Rodents

Field Mice (Voles)

Field mice, also known as voles, are smallrodents (about 13 to 23 cm long) with small,furry ears and relatively short tails. They fre-quently gnaw the bark of trees and shrubs, andcan damage underground plant parts by theirtunneling and chewing. Voles can tunnel underand chew through plastic ground liners causingdrainage problems and contamination of the re-circulation system.

Cultural ControlField mice avoid areas that do not provideadequate cover from predators. Removal ofgrass and weeds adjacent to the greenhousewith herbicides or frequent mowing will reducethe number of mice in the area. Sawdust andused media on soil or on plastic liners, provideprotected habitat for field mice and should notbe piled near the greenhouse.

Poison BaitsPoison baits must be placed in covered baitstations to protect them from the weather and toprevent accidental poisoning of other animals.Bait stations can be easily built from metal orplastic pipes, tin cans, and pieces of wood, ormay be purchased commercially. However,outdoor bait stations must be secured againstlocal dogs as they will learn how to upset thestations to get at the bait and by the time yourealize what has happened, it will be too late.Bait stations should be placed at 3 to 4 mintervals in areas where there are signs of mouseactivity. The disappearance of the contents willindicate that mice have fed on the baits.

Use one of the following according to labeldirections:

• diphacinone (Ramik Brown) (multiple-dose;highly toxic to dogs); or

• chlorophacinone (Rozol) (multiple-dose);or

• zinc phosphide (Mouse Bait 2, ZP, Z-phos)(single-dose).

House Mice and Norway Rats

The house mouse, found nearly throughoutB.C., is a small rodent (16 to 18 cm long),differing from the field mouse by having alonger, naked tail, larger ears, and a morepointed snout. The Norway rat or brown rat,found in coastal areas only, is a much largerrodent (36 to 40 cm), which also has a long,hairless tail. Both house mice and rats mayinvade indoor facilities. Although they some-times damage growing plants and fruits, theyare mainly pests of stored food products, andare also undesirable because they can carry anumber of diseases, which can be transmittedto humans. They may damage plastic groundliners causing drainage problems and contami-nation of the re-circulation system.

Rats and mice are rarely seen unless very numer-ous, but can be detected by the following signs:

• droppings (cylindrical and about 5 to 20 mmlong with rounded ends in rats, versus about3 mm long with pointed ends with mice);

• sounds (gnawing, squeaking, scampering);

• tracks on dusty surfaces or in snow;

• evidence of burrows or holes;

• runways and greasy rub marks along wallsand pipes;

• damage to young plants or fruits.

Cultural ControlRodent-proofing buildings and eliminatingsources of food, water, and shelter are the bestmeans of control. Trapping and poisoningprovide only temporary relief. Buildings can bemade rodent-proof by installing tight-fittingdoors and windows, and wire screens overbasement windows and vents. Metal doors orsheet metal kick-plates on wooden doors willstop rodents from gnawing through. Elimina-tion of nesting areas through good housekeep-ing prevents rodents from getting establishedand reproducing. Never leave piles of paper,burlap, styrofoam, etc., especially against wallswhere you can’t clean regularly. All food, feedand seed, including slug bait should be kept in


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rodent-proof metal containers. Old chest-typefreezers are good for this purpose. Garbagecontainers in or near the greenhouse must berodent-proof and have tight-fitting lids.

Poison BaitsNumerous rodenticides are available for con-trolling house mice and Norway rats. Becauseof the wide variety of trade names forrodenticides, only the common names are givenbelow. All of the poisons listed, except for redsquill, are registered for control of both housemice and Norway rats.

Use one of the following according to labeldirections.

Multiple Dose :

brodifacoum;or bromadiolone;or chlorophacinone;or diphacinone (highly toxic to dogs);or warfarin (may also include ergocalciferol

or sulfaquinoxaline).

Anticoagulant rodenticides may require severalfeedings to ingest a lethal dose, but eventuallycause death from internal or external bleeding.The most potent anticoagulants arebromadiolone, brodifacoum, chlorophacinone,and diphacinone; however, less toxic anticoagu-lants such as warfarin (alone or with otherchemicals) may also give adequate control, andare less hazardous to domestic animals. Re-peated use of the same class of product with-out achieving control indicates that the localpopulation of rodents is resistant. Switching toa product with a different chemical structuremay be necessary.

Single Dose:

zinc phosphide;or red squill (rats only).

Acute rodenticides such as zinc phosphide andred squill are more toxic, and can cause deathafter a single feeding. Covered bait stations,recommended for all rodenticides, are essentialwith single-dose rodenticides if there is anypossibility of other mammals or birds havingaccess to the treated area.


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Disease ManagementPlants become diseased when attacked bycertain pathogens: fungi, bacteria, viruses ornematodes. The first step in any disease man-agement program is proper diagnosis to deter-mine the cause of the problem followed by anunderstanding of the disease cycle. Alwaysidentify and confirm the cause of the plantproblem by sending a sample to a local plantdiagnostic lab. Do not assume a disease-causingagent is responsible for the problem that couldbe due to environmental factors.

It is important to know which conditions influ-ence disease development when managing thehealth of plants. The three major conditions thatcontribute to the development of a plant diseaseinclude a susceptible host plant, a pathogen

and an environment that is favourable for thepathogen and/or unfavourable for the host. Ifthese three factors are all present in a green-house, a plant disease is likely to result. Under-standing these three factors will help in consider-ing appropriate control measures.

Good disease management involves using allavailable tools to prevent and reduce diseasedevelopment. This means utilizing crop moni-toring; and cultural, physical, biological andchemical control strategies. Disease preventionis the best management strategy to follow.Keep plants healthy by following good culturalpractices such as strict sanitation and suitableenvironmental control.

Crop Monitoring – Examine transplants fordisease symptoms before they are brought intothe greenhouse. It is easier to prevent newinfections than to control established ones.Prevention is the best disease managementstrategy. During the growing season, monitoringshould be done weekly as a minimum. Workersare in close contact with the crop so they canspot problems early. Train them to be on thelookout for symptoms of disease and abnormalgrowth, as well as pest outbreaks.

Cultural Control – means promoting growingconditions that favour good crop growth and,where possible, manipulating conditions to thedetriment of the pathogen. Fungi and bacteriatend to prefer warm, humid conditions. Discour-age moisture condensation on the crop by gradu-ally raising temperatures prior to sunrise. Main-tain adequate temperatures in the root zone. Forexample, keep root zone temperatures above20ºC to reduce Pythium root rot. Provide ad-equate spacing of plants and ventilation toreduce relative humidity. Provide optimumnutrition. Use resistant varieties or rootstockswhere practical. Allow sufficient time betweencrops to do an adequate cleanup. Practice goodsanitation (see Sanitation, page 129).

Physical Control – uses agents such as hightemperatures to affect the pathogen. Heat-treating rockwool slabs is one example. Usescreens and sticky traps to control insects thatcan vector viruses and spread certain fungi.

Biological Control – uses nonpathogenicfungi, bacteria, viruses and nematodes tocontrol plant pathogens. Unfortunately, thereare few biological control agents registered fordiseases in Canada. Current registrations ongreenhouse vegetables include Mycostop (Strep-

tomyces griseoviridis), Rootshield (Trichoderma

harzianum) and Sporodex (Pseudozyma flocculosa

strain PF-A22).

Chemical Control – means using fungicidesonly when necessary as determined by cropmonitoring. Select those fungicides that are nottoxic to biological control agents. Check withyour supplier before using a new product.Rotate fungicide groups to reduce the possibil-ity of the development of disease resistance.Use the recommended rate. Too low a fungi-cide concentration could select for resistantfungi populations.

Fungicide Resistance

Fungi have genetic variability and in everypopulation there will be some individuals thatare less affected by a fungicide. Fungi thatproduce large numbers of spores, e.g. Botrytis,


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are more likely to develop resistant populationsbecause there is a greater chance for geneticdiversity with larger numbers. Most fungicideresistance develops by selection pressure onthis very small group of the fungus population.Susceptible fungi are killed when a fungicide isapplied at the correct rate. This leaves lesscompetition for food for the resistant fungi,which will then flourish. If the same fungicideis applied again to control this population, therewill be little or no control.

Fungicides work by affecting one biochemicalprocess (site-specific) or several biochemicalprocesses (multi-site) of the fungus. It takeslonger for resistance to develop with the lattergroup. It is recommended not to use oneproduct, especially of the specific type, con-tinually or resistant populations may build up.Use fungicides from different chemical groupsas each group has a different mode of action.Use the recommended label rate. Lower ratescould cause resistance to develop by allowingpopulations of less sensitive strains to surviveand increase. Using higher rates could causecrop damage or excessive residues.

Fungal Diseases of

Sweet Pepper

Damping-Off (Pythium spp.,Rhizoctonia solani)

Biology and Disease CycleDamping-off, caused by Pythium and Rhizoctonia,

is a common disease affecting seeds, seedlingsand roots of many greenhouse crops. Peppersare especially susceptible to damping-offbecause of their slow germination and emer-gence. Seeds rot and seedlings are killed beforeor just after emergence (pre- or post-emergencedamping-off). Growth and yield in older plantscan be severely reduced due to crown and rootrot. Pythium species, close relatives of fungi, areclassified as protists or water moulds that growin water and soil by producing microscopic,thread-like strands and swimming spores thatinfect plant roots. The soil fungus, Rhizoctonia

solani, does not commonly have a spore stage.Rhizoctonia also grows in the soil by producingmicroscopic thread-like strands that directlyinfect plant roots. Both microorganisms surviveby producing resistant structures. Rhizoctonia

forms tiny, black, pepper-like survival struc-tures called sclerotia while Pythium formsresistant, thick-walled, resting spores calledoospores and chlamydospores. Both organismscan survive in crop debris. Pythium can alsosurvive and spread in water.

Sanitation, good cultural practices and suitableenvironmental controls are the most effectivedisease management strategies for damping-off.The disease is triggered by conditions thatfavour soft vegetative growth including adverseroot and irrigation temperatures (too low or toohigh), low light levels, warm growing condi-tions (above 28°C) and low O

2 levels in the

growing media (saturated growing media).

Disease SymptomsPoor seed germination is often a result of seedrot caused by Pythium. Seedlings are also fre-quently infected resulting in wilting and prema-ture collapse of the seedling before or aftercotyledons open. Typical Pythium infections arecharacterized by brown discolouration andconstriction at the soil line at the base ofseedling stems. Infected roots often appearwater-soaked, discoloured and rotted, particu-larly at the root tips.

Management Strategies

Sanitation• Follow a strict, year-end sanitation program

by disinfecting greenhouse structures, equip-ment, tools and other materials that maycontact plants.

• Use healthy, disease-free transplants.

• Provide good drainage and avoid excessmoisture in the growing medium.

• Use pathogen-free water.

• Rogue out infected plants when they are first


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detected. Place them directly in a plastic bagon the spot and remove them from thegreenhouse.

Cultural Control• Maintain optimal growing conditions, espe-

cially for seedlings and younger plants.

• Provide sufficient space for plants. Do notovercrowd seedlings.

• Water seedlings in the morning so they candry off during the day.

• Ensure that day storage tanks are cleanedand water from dugouts or rain collection isproperly disinfested and treated for disease-causing microorganisms.

• Exercise care when transplanting (‘flipping’)seedlings. Let seedlings wilt slightly so thatstems bend easily and are not wounded whentransplanting.

• Promote good germination and avoid ad-verse temperatures that slow germinationand seedling growth (i.e. avoid media tem-peratures below 20-23°C and irrigationtemperatures <18°C).

• Control fungus gnats and shore flies thatspread the pathogens.

• Minimize plant stresses.

Biological Control

Seedling treatment –

Use Mycostop, (Streptomyces griseoviridis) at theseedling stage at 1 gram/10 L of water tomake a 0.01% suspension and apply it at 0.2to 1.0 L/m2 of seedlings. Do not use

Mycostop as a seed treatment.

Transplanting treatment –

At the transplanting stage use Mycostop at1 gram/2 L of water to make a 0.05% sus-pension. Apply it at 20-100 mL per plant andrepeat every 3 to 6 weeks.

Chemical Control (at propagation only)

Seed treatment –

Use seed treated with a fungicide or treatwith Thiram 75 W at 0.004 grams per gramof seed. Caution: Do not consume alco-

hol immediately before or within 24 hours

after working with Thiram. Captan dustcan also be used to treat seed. Customizedseed treatment with specialized seed equip-ment is required when applying these smallamounts of fungicides.

Treatment of rockwool blocks –

If damping-off occurs, soak blocks with asolution of:Captan 50 WP at 25 g/10 L water, orCaptan 80 WP at 15 g/10 L water, orMaestro 75 DF at label rates.

Transplants –

For late damping-off or seedling root rot,drench plants withMaestro 75 DF (captan)at 15 g/10 L ofwater orNo Damp (oxine benzoate) at 100 mL/10 Lof water.


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Fusarium Stem and Fruit Rot,(Fusarium solani,perfect state = Nectria haematococca )

Biology and Disease CycleFusarium solani is a common soil-borne fungusexisting in many different races. The one causingstem and fruit rot of greenhouse peppers canresult in serious plant and fruit losses, especiallyin the spring and early fall. Spores are suspectedof being carried on the seed surface and are alsospread by soil, media and drain water. Airbornespores called ascospores (produced by theperfect state), spread the disease within a peppercrop. Fusarium commonly enters the plantthrough wounds created by basal stem growth,root pressure, pruning and stem clips. The moistsurface of rockwool cubes is ideal for germina-tion and growth of the fungus. Nutrient feed andplant root exudates are energy sources for thefungus. Fruiting bodies are formed on the sur-face of rockwool blocks. Water is taken up bythe fruiting bodies and spores are forcibly shotinto the air. The location of the fruiting bodieson the moist blocks means that spore dispersal islargely temperature dependent and independentof the greenhouse relative humidity. Spores arereleased under conditions of RH < 83% whichis usually after midnight. Although fungal fruit-ing bodies are visible only on the surface of thecubes, the vegetative part of the fungus, (hyphaeand mycelium), grow throughout the cubes.There is potential danger that the fungus willinfect adjacent young roots, grow up the mainroot and invade the crown. Fallen or abortedfruit can also become infected and act as sourceof inoculum. Warmer temperatures, approxi-mately 28ºC, favour the disease. Developmentand spread can take place very rapidly in thesummer. Inoculum (spores) builds up in thespring and fall when VPDs are lower. Stressedplants with high fruit loads are more susceptibleto attack by low sugar pathogens like Fusarium.Plants that are grown vegetatively tend to bemore prone to infection. Irrigation managementthat favours root pressure can increase the riskof infection from wounding.

Disease SymptomsThe first inoculum evidence of the fungus isoften the red fruiting bodies found on the rockwool block. On the plant; soft, dark-green toblack lesions form at stem or fruit nodes or leafpruning wounds. Lesions first occur at thebottom of the stem close to the fork where thetwo stems split. The callous tissue in this areais easily wounded when the support strings aremoved, creating a hairline crack where sporesenter. Lesions enlarge and eventually girdle thestem. Pepper fruit also becomes infected aroundthe calyx especially if it is damaged or over-ripe.Fruit can rot in storage. Rotted tissue is sunken,dark-brown to black, with tiny red or orange-pink fruiting bodies. Plants with infected stemsexhibit symptoms of nutritional disorders andproduce end-of-season fruit with uneven ripen-ing. See colour photos 42 & 43.


Sanitation• Follow strict year-end sanitation. Refer to the

section on Grey Mould, page 117.

• Ensure clean irrigation lines and dripperstakes at the start of the season. Sampling ofirrigation lines has shown survival ofFusarium spores when traditional cleanuppractices are used. It is important to pres-sure flush organic matter prior to chargingthe lines with cleaning agents such as buff-ered bleach or Virkon.

• Prevent entry of disease into the greenhouseby using foot-baths and seal the floor plasticcompletely so that soil is not exposed.

• Do not re-use bamboo stakes if stem andfruit rot was severe. The fungus has survivedon stakes dipped for 24 hours in a 300 ppmsolution of sodium hypochlorite.

• Cover trash and cull piles of rotting vegeta-tion with a tarp or soil and locate them at adistance downwind from the greenhouse.


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• Avoid wounding the plug transplant bylimiting the ‘flipping’ process to a 45 to 90o

angle when transplanting into the block.

• Regularly clean tools, especially pruningknives with a disinfectant. Follow properpruning methods by making a clean cut thatheals quickly without leaving ragged edges orstubs.

• Promptly remove infected plant and fruit bydirectly placing in a poly bag and removingthem from the greenhouse. Infected fruitlying in the drain gutter can spread spores viathe return nutrient solution.

Environmental Control• Avoid over-use of screens at the start of the

crop. Ensure adequate VPD > 3 and avoidscreen use when the outside night tempera-tures are > 10°C. This prevents the develop-ment of large vegetative cells. These thin-walled cells are especially prone to fungalinfection.

• Avoid over-use of roof sprinklers that causedripping on the plants especially under hightemperature conditions > 28°C.

• Select temporary screens with more holespacing, 10 x 10 cm, and manual openingcontrols or cut larger ventilation holes as ameans of controlling condensation.

• Use EC of 3 to 3.5 with Ca drain levels of 7- 8 millimoles/L in establishing the plant anddeveloping stronger stem cells resistant tothe disease.

• Avoid root pressure conditions caused byirrigation too early in the day.

• Attempt to grow plants at a uniform rate.Crops that are grown rapidly tend to be softand are more prone to Fusarium. However,long periods of stress or a growth slowdownshould also be avoided.

• It is important to maintain good air circula-tion within the canopy and at the base of thecanopy with a minimum rail pipe of 40°C.The pipe can be removed at light thresholds

over 300 w/m2. This is especially importantfor rows running east-west in spring and fallwhen the sun does not reach the pathways,creating microclimates that favour diseaseinfection.

• V-System of training and stem densities > 7has the disadvantage of creating high humid-ity within the vertical canopy leading to agreater risk of stem infection.

• Disease outbreaks are controlled by strictsanitation and aggressive climate controlusing 24 hour minimum pipe and keepingtemperature <28°C and VPD >3.

• Stem lesions can be scraped away in the earlystages of infection. Apply a drying agent likehydrated lime to prevent stem girdling.

• Before plant death occurs, replacement sideshoots from adjoining healthy plant can beinitiated to maintain plant density.

Biological ControlMycostop (Streptomyces griseoviridis)

Use seedling stage drench or irrigationmethod.

Mycostop is a biological antagonist contain-ing a beneficial soil bacterium, The beneficialbacteria colonize plant roots depriving thedisease of living space and nourishment andsecreting inhibitory enzymes and metabolites.Mycostop must be established in the seedlingstage, prior to the onset of disease as apreventive treatment. Ensure there is acarbon source like bran to allow establish-ment in the inert rock wool plug. Add a mixof ‘used’ sawdust and peat moss to the topof the block before hand drenchingMycostop or applying through the irrigation.Follow label directions and rates (see alsowriteup under Damping-off, page 113).

Chemical ControlNo chemical fungicides are available forFusarium stem and fruit rot of pepper.


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Grey Mould (Botrytis cinerea)

Biology and Disease CycleGrey mould, caused by the fungus Botrytis cinerea,

infects weak, injured or dying parts of green-house crops and most outdoor herbaceousplants. Above-ground plant parts such as spentflowers, injured leaves and stems, especiallypruning wound stubs, are ideal for grey moulddevelopment. Stem infections can kill plants androtted fruit is unmarketable. Disease develop-ment requires moderate temperatures, highrelative humidity and/or the presence of water.

Over-winter survival of the fungus is by tinysclerotia; hard, black, pepper-like resting bodiesoften found in crop debris. Microscopic, air-borne spores are the primary means of diseasespread. Spores are seed-like propagules thatsurvive 20 – 30 days in the greenhouse. Air-borne spores enter through greenhouse vents oron infected plants and debris. Disease spreadswithin the crop by airborne spores, workeractivity, CO

2 tubes, water splashing and drip-

ping condensation. Insects can also help spreadthe disease. Cultural practices such as pruningand harvesting disturb the crop, creatingwounds and spore showers.

Grey mould development is closely associatedwith environmental conditions. Warm tempera-tures, high humidity or the presence of water isnecessary for rapid spore germination andinfection (see Table 5-10). Grey mould sporeproduction is best under ultraviolet light (wave-length 355 nm).

Botrytis on stems may show no symptoms forseveral days or weeks until there is a physi-ological change in the plant tissue. Such latentinfections can first appear in spring at pickingwhen symptoms are manifested. Shifts incarbohydrate levels can cause an increased riskof infection. Fruit load changes in late springand early fall can result in carbohydrate shiftsfrom the fruit to the stems and leaves encour-aging grey mould infection in those areas.

Disease Symptoms

Spring

Infection starts as a water-soaked spot or decayof petals, leaves, stems and fruit. The classicgrey mould lesion is brown with a fuzzy greygrowth of spore masses often arranged inconcentric bands. Grey mould stem infectionsare the same as those found on tomatoes andcucumbers. (See colour photo 44.) In earlyspring, injured leaves or stems can becomeinfected with grey mould. Old flowers initiatenew grey mould infections when they fall offand come into contact with healthy planttissue. The dry flower tissue is an excellenthygroscopic growing media and will absorbwater vapour from the air even at RH < 80%.

Fall

Grey mould is prevalent again in the fall onyoung leaves within the head of the plant or onstems wounded by carts and leaf pruning scars.Under humid conditions, diseased tissue be-comes covered in grey masses of spores. Fruitinfection is similar to Erwinia soft rot butwithout the associated odor or bacterial decay.

Table 5-10. Environmental factors favourable to disease development by Botrytis

Disease cycle stage Temperature °C Relative Humidity % Vapour Pressure Deficit

Infection 15 - 18 > 80 < 3

Development range 0 - 30

Rapid colonization 25 - 30 > 80 3 - 8

Conidia development 15 > 80 < 3

Spore release > 15 60 -100 1 - 5


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Sanitation• Reduce grey mould by preventing the build

up of Botrytis spores on greenhouse plantsand debris and on outdoor trash piles androtting vegetation.

• Follow a strict, year-end sanitation programby disinfecting greenhouse structures, equip-ment, tools and other materials that maycontact plants. Be sure to eliminate all plantdebris that might carry disease over to thenext crop. Power wash the interior green-house surfaces including the glass and allinside structures including screens, pipes,and troughs. Use a cleaning solution on cartsand tools. Following power washing, apply asurface disinfectant wash of 1% Virkon orChemprocide 8ml/L. Eliminating 90% ofthe disease inoculum can reduce the inci-dence of disease from 60% to 10%.

• Use healthy, disease-free transplants.

• Select cultivars that are less sensitive toBotrytis infection.

• Make every effort to remove prunings, deador dying plant material and rotting fruitpromptly from the greenhouse before sporeshave a chance to form. Remove infectedplant parts when first detected by placingthem, on the spot, in a plastic bag for dis-posal away from the greenhouse.

• Follow proper pruning methods by making aclean cut that heals quickly. Do not leave aragged edge or stub.

• Keep trash and cull piles of rotting vegeta-tion covered with a tarp or soil and at adistance downwind from the greenhouse.

• Regularly clean tools, especially pruningknives with a disinfectant.

• Provide foot-baths to prevent carrying dis-eases into the greenhouse.

Cultural ControlA healthy crop with minimal stress has reducedrisk of disease infection. In spring and fallminimize crop stresses resulting from irrigation,climate, fruit loads, and pests. Higher humidity,reduced fruit loads and shorter days in springand fall can trigger grey mould. Do not allow

condensation to form or drip onto plants.

Dew point management to prevent the forma-tion of free water prevents development ofgrey mould conditions.

• Reduce the RH variability by ensuring calibra-tion and uniform distribution of psychrometersensors maintaining RH < 80%

• Avoid cold air dropping onto heads whenventing if outside temperatures are below12°C and greenhouse gutters are less than4.5 meter. The cold air dropping on theheads can cause condensation on the leafand head tissue promoting Botrytis infection.Energy losses from night radiation fromheads and tissue can also increase wetnesson the leaves and promote infections.

• Maintain good air circulation within thevertical crop canopy to reduce humidity. Usea minimum pipe of 40°C and a grow pipelocated 50 to 60 cm below the head. Removeonce light levels > 300w/m2.

• Under RH > 90 % conditions, avoid the dewpoint being reached because of rapid tem-perature ramping. Ensure the leaves are dryby heating up three hours prior to sunset toevaporate any free water.

• Under RH > 90%, avoid excessive conden-sation dripping from the glass by using aminimum vent. The calyx end of the fruitcan collect moisture which is an ideal infec-tion site. Fruit later rots and drops off.

• Ensure adequate EC > 2.5 and target opti-mum calcium levels (6-7 millimoles) and lowrange nitrate (15-18 millimoles) levels espe-cially in the spring and fall.

• Avoid or reduce plant handling on dull dayswith high RH. These conditions favour


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infection, especially when high spore num-bers (inoculum loads) result in spore showerson plants.

• The most effective control strategy for an

outbreak of grey mould is to create a

climate with RH < 80% and VPD > 3.

Chemical Control

Captan (Seedling treatment only)

Captan is a broad-spectrum fungicide thathas protective and eradicative properties butis not systemic. On peppers, captan is onlyregistered for use in the seedling stage.Weekly sprays help prevent infections underhigh disease pressure (spring/fall) but willnot control established or latent infections.Formulations vary; read the label to deter-mine rate of application.

Powdery Mildew(Leveillula taurica)

Biology and Disease CyclePowdery mildew on greenhouse peppers causedby the fungus, Leveillula taurica, was first re-ported in Ontario in 1999 and in B.C. in 2003.It is a different species from the one that infectscucumbers. Like other powdery mildews, it isan obligate parasite and will grow only on livingtissue. However, this mildew is unique in thatthe mycelium grows inside leaves and thetypical white powdery growth on top of leavesis not present. The disease can be cyclic inseverity showing up one year and then disap-pearing for several years. This species alsoinfects tomatoes, onions, sunflowers, severalfield crops and some weeds. There may besome strain specificity limiting spread from onehost species to another.

Wind currents disperse spores and high humid-ity favours spore germination. Pepper powderymildew infection can occur over wide tempera-ture ranges (19 – 33°C) under high and lowhumidity ranges. Pepper powdery mildew isreported to infect peppers under humid condi-tions; whereas in tomato, infection occurs

under dry conditions. Secondary infectionoccurs every seven to ten days so it is impor-tant to regulate the timing of spring programsto prevent rapid spread.

It is very important that mildew infectionsnever get out of hand because higher infectionlevels cause greater yield loss. Research in theNetherlands has shown that for every 1%increase in infection during the growing season,there is a 1% decrease in yield. In Europe,early heavy infections of powdery mildew havecaused losses of 30%, compared to later andlighter infection. Since mildew clearly hasnegative effects on production, even from lateinfection, the object is to limit the infection asmuch as possible.

Disease SymptomsWhite to light grey spots first occur on theunderside of older leaves located inside theplant canopy. Leaf infections become yellowor appear as raised pimply areas at correspond-ing locations on the upper leaf surface. Theseearly yellow symptoms sometimes resemblespider mite damage. Severe infections causeyellow/brown discolouration with mildewpatches moving to the upper leaf surface.Infected leaves will eventually curl and dropresulting in the exposure of fruit to sunscald.The severity of leaf drop varies not only withthe intensity of mildew infection but also withvariety. The resulting reduced plant vigor canbe severe. Fruits and stems are not normallyinfected.


Sanitation• Take added precautions to avoid introducing

powdery mildew into your greenhouse espe-cially if you have recently been visitinggreenhouses outside B.C. Diseases can becarried on clothing, shoes, soil, and espe-cially infected plants.

• Follow a strict, year-end sanitation programby disinfecting greenhouse structures, equip-ment, tools and other surfaces that contact


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plants (refer back to the writeup on GreyMould, page 117).

• Use healthy, disease-free transplants that aregrown locally.

• Control weeds around the greenhouse.

• There are no resistant varieties of peppers.

Chemical ControlEarly, preventive measures are essential toprotect young plants before infection. Powderymildew is difficult to control once leaves be-come heavily infected. Treat with alternatingsprays of the following fungicides as soon aspowdery mildew is detected. Note: Cautionneeds to be taken when using the followingfungicides as plant damage may result, espe-cially under high temperatures.

Sulphur

Use Bartlett Microscopic Sulphur 92% as aprotectant fungicide applied prior to powderymildew infection.

Apply 540 to 760 grams of the 92% product/haas a high volume foliar (1,500 – 3000 L water/ha), spray when powdery mildew is first de-

tected. Ensure thorough coverage of thefoliage, especially the lower leaf surface. Con-sider applications in late evening when it iscooler to reduce possible leaf injury. Use nomore than ten applications per crop cycle. Applyon a minimum interval of 14 days. Do not

enter or allow unprotected workers to enter

into treated areas until 24 hours after appli-

cation.

Nova (myclobutanil)

Nova 40W is used as a systemic protectantand curative fungicide.

Use 340 grams per hectare in 1,500 – 3,000L of water/hectare when powdery mildew isfirst detected. It is important to apply highspray volume to ensure good coverage in-cluding the lower surface of the leaf. Alter-nate the Nova spray with a sulphur spray toavoid possible resistance. Use a maximum of

three Nova applications per crop cycle.Follow all label directions as possible hormo-nal side effects can occur that can set backplant development and production. Do not

apply within 3 days of harvest. Do not re-

enter treated areas within 12 hours of

application.

White Mould(Sclerotinia sclerotiorum)

White mould, common in field vegetables, canalso occur in greenhouses if soil becomesinfested with the fungus (Sclerotinia sclerotiorum).

The white mould fungus can persist in the soilfor years causing infection in subsequent crops.Cucumbers and tomatoes are also susceptible.

Biology and Disease CycleWhite mould can cause pre or post-emergencedamping off of young seedlings but morecommonly attacks the crown, stem and fruit ofplants. Large (5 - 8 mm), brown to black,resting structures called sclerotia form withinrotted stems. Sclerotia are long-lived and sur-vive in soil and diseased plant tissue. Sclerotiagerminate within the soil surface and formvegetative strands (hyphae or mycelium) thatinfect nearby plant tissue. They also producefruiting bodies that release tiny ascospores thatare carried long distances on the wind.

Disease SymptomsA black lesion covered with a dense fluffywhite fungal growth usually characterizes whitemould infections. The lesion eventually girdlesthe stem and kills the plant above that point.Sclerotia eventually develop in the rotted pithcavity of infected stems (see colour photos 45& 46).


Sanitation• Remove infected plants and plant parts from

the greenhouse promptly before the sclerotiaform. Sclerotia continue to develop after theinfected parts have been removed and willadd to the inoculum level in future years.


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• Remove cull and trash piles from the vicinityof the greenhouse and cover or bury deeply.

• Provide foot-baths to prevent bringinginfested soil into the greenhouse.

• In greenhouses with a history of whitemould, thorough end-of-season cleanup andlaying of new plastic ground liner is advisedprior to the next cropping cycle.

Cultural Control• In the south coastal area of B.C., avoid

growing sunflowers, cucurbits or beans closeto the greenhouse as they are all very suscep-tible to white mould in humid areas andcould raise the inoculum level in the vicinity.Ascospores move easily on wind currents.

• Well-managed greenhouse crops that are keptfree of condensation and/or dripping waterare rarely infected by white mould.

Storage Rots

Biology and Disease CyclePencillium, Rhizopus, Fusarium and other fungiinfect stored pepper fruit under less than idealconditions. Infections occur when fruit is wetfrom dump grading or condensation and there isinadequate box ventilation. Storage rots can bea problem early in the spring when fruit cellwalls are not as strong as fruit produced in thesummer. Poorly developed flowers that aregrown under low light and low temperatureshave a tendency to create fruit imperfectionsthat can be infected by Fusarium and otherfungi. Internal fruit rot that develops is difficultto detect at grading.

Integrated Disease Management

Cultural Control• Keep plants healthy by following good

cultural practices such as strict sanitationand proper environment control.

• Maintain active growing climates at all timesespecially during early crop development.

• Avoid over-using screens in the spring whichcan lead to weak flowers prone to fruitstorage rots.

• Maintain active pipe climates (40 - 55oC)especially in early/late fall when the planthas a full canopy.

• Water dump tanks must be kept clean toprevent the spread of fungal and bacterialinoculum. Chlorination of the tank water at100 ppm followed by a spray rinse of potablewater is recommended.

Bacterial Diseases ofSweet Pepper

Bacterial Soft Rot(Erwinia carotovora)

Biology and Disease CycleThe bacterium, Erwinia carotovora, causes soft rotof stems while infection of pepper fruit is prima-rily a post-harvest disease. The disease is not amajor problem but can show up in early spring orlate fall when low VPD favours its development.Soft rot is often spread when pepper fruits arewashed before packing. Post-harvest infectionsare particularly damaging on fresh market peppersas infected fruits rot and spread the decay to therest of the fruit in the container.

In field-grown peppers, infections occur duringrainy weather when soil splashes onto suscepti-ble fruit. High moisture content predisposesfruit to soft rot infection. The bacterium canonly enter the plant through wounds, particu-larly those created by insects. Harvested fruitsare infected through the stem end, wherecrevices catch and hold moisture.

Disease SymptomsBacterial soft rot symptoms closely resembleFusarium stem and fruit rot (see page 115).Stem infections show internal darkdiscolouration of the pith and sometimes thevascular tissue. The fruit infection often startsat the stem or areas around fruit wounds that


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become sunken, and the internal tissue softensquickly to the point of complete collapse. Thetissue fluid collects in the lower portion of thefruit, which expands and eventually ruptures.This watery rot is accompanied by a foul smell.Fruit infected in the field tends to collapse andhang on the plant like a water-filled bag. Whenthe contents leak out, the outer skin of thefruit dries and remains attached to the plant.


Sanitation• Keep plants healthy by following good

cultural practices such as strict sanitationand proper environment control.

• Follow a strict, year-end sanitation program bydisinfecting greenhouse structures, equipment,tools and other surfaces that will contact plants(see Grey Mould, Sanitation, page 118).

• Remove infected fruit from the plant or floorand place in a plastic bag for disposal.

• Avoid using harvest knives to remove in-fected fruit unless they are sterilized aftereach use. Work infected area last as thedisease can rapidly spread on workers’clothes, tools and hands. Picking fruit whenit is dry, avoiding injury during handling, andcool storage reduces post-harvest decay. Iffruit is dumped in a water bath after harvest,the tank should be flushed, disinfected andre-filled daily. The tank water should bechlorinated to 100 ppm. The fruit should bespray rinsed with potable water and driedpromptly after exiting the water bath.

• Some producers have found that vacuumcooling after harvest slows bacterial soft rotstem-end decay in transit.

Virus Diseases ofSweet PepperViruses are extremely small particles that aremade up of nucleic acids surrounded by aprotein coat. They can be seen only with an

electron microscope but can be detected byseveral different laboratory techniques includ-ing: indexing to sensitive indicator plants;antibody-antigen reactions (serology); andDNA comparison with known viruses. Virus-infected plants exhibit a range of symptomsfrom none (latent) through leaf mottling, leafmosaic patterns, etiolation, deformities, stunt-ing and sudden death (shock). Some virusescan be transmitted on seed (usually on the seedcoat); some require physical contact withinfected plant sap on tools, hands, etc.; somerequire vectors, such as aphids that move virusparticles from infected to healthy plants whilefeeding. Control strategies involve regular cropmonitoring, prompt removal of infected plants,careful crop handling practices, use of resistantvarieties and vector control. Correct identifica-tion of the virus is important in order to deter-mine the appropriate control measures, e.g.whether vectors need to be controlled.

Pepper Mild Mottle Virus(PMMV)

Biology and Disease CyclePMMV is related to tobacco mosaic virus andmay be introduced on infected seed, trans-plants, plant sap and plant debris. There are noknown insect vectors of this virus. PMMVspreads easily from plant to plant during thecourse of transplanting and tending the crop atall growing stages.

Disease SymptomsSymptoms of PMMV are not readily visibleuntil fruit production. Symptoms to watch forinclude mild stunting, slight leaf yellowing anddark and light green mosaic patterns on theleaves. Foliar symptoms on new growth can bemistaken for other disorders such as temporarymagnesium or manganese deficiency. Fruitsymptoms include distinct bumps, pointed tipsand sunken brown areas primarily at the calyxend and flower ends. The brown areas seem tostart in a crease at the calyx and move downthe fruit. Colour streaking may also occur. Seecolour photos 47, 48 & 49.


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Management Strategies• Use virus tolerant cultivars (TM2, TM3

resistance).

• Use only healthy transplants and discard anyweak plants. Rogue suspicious plants earlybefore routine maintenance begins. Do notmix new plants or plants from differentsources with older plants.

• When handling seedlings, spray them with a10% solution of skim milk powder contain-ing at least 35% protein. Use 100 grams oflow fat milk powder per litre of water. Handsmust be dipped in the skim milk solutionbefore handling the plants and when workingwith the plants. Hands should be dippedbetween each plant.

• Always work the plants in the same directionto prevent spread.

• Practice good sanitation by cleaning shoes,boots, tools, rubber gloves and clothes.

• Use foot-baths of quaternary ammonia orother viricide products at the entrance of thegreenhouse.

• Restrict visitor access to the header walk-ways only and do not allow the crop to behandled.

• Remove all crop debris at the end of thecropping season. Haul it away or bury it. Thevirus can survive in dry plants for as long as25 years.

• Pressure wash the entire greenhouse interior.

• Pressure wash all carts, totes, and tractors,especially tires.

Tobacco Mosaic Virus (TMV)and Tomato Mosaic Virus(ToMV)

Biology and Disease CycleThese viruses are closely related and displaysimilar symptoms. There may be some differ-

ences in the usefulness of resistant cultivars,depending on which strain is present. Thefollowing description and control strategy,while written for TMV, applies to both. Thesediseases can cause stunting, reduced yields andreduced fruit quality.

TMV is spread easily by handling during trans-planting, tying and pruning. It is soil-borne,seed-borne and survives in infected plantresidue. It can survive in root debris for over22 months. Spread can also occur from con-taminated clothing. The virus may remaininfective for years on unwashed clothing keptin the dark. TMV has also been shown tospread through gutation fluid at the tips ofleaves. Climate controls that promote rootpressure could aggravate spread by this mecha-nism. TMV infects a very wide range of plantgenera.

Disease SymptomsSymptoms vary depending on the strain of thevirus, host cultivar, environmental conditions,and the presence or absence of other viruses inthe same plant. TMV first appears as necrosisalong the main veins with wilting and leaf drop.Later growth may be distorted with a mosaicpattern. Fruit is mottled and may have necroticspots.

Management Strategies• Use virus resistant cultivars (TMV, TM2,

TM3 resistance).

• Be especially cautious of older cultivars likeEagle that do not have TMV resistance.

• When growing susceptible cultivars, use one-year-old seed. One to 2 days before sowing,soak the seed for 15 minutes in a 10% solu-tion of trisodium phosphate (100 g / L),rinse thoroughly and spread out to dry. Seedcan also be heat-treated at 70°C for 4 days.

• Handle plants as little as possible and re-move any plants with mosaic symptomsshowing up early in the season. Later in theseason, there is no benefit to removing


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infected plants as the virus will have spreadand there will be latent infections(symptomless plants) throughout the crop.

• Dip hands in milk before handling the crop ifan infection is suspected. Wash handsthoroughly with soap and water to inactivatethe virus after working with infected plants.Work in infected areas last.

• Spray seedlings with skim milk solutioncontaining at least 35% protein (add 100 gpowder to 1 L water) the evening beforetransplanting or handling.

• Do not smoke near plants or in the green-house as tobacco products can carry thevirus. Wash hands thoroughly with soap andwater after using tobacco products.

• Use only new seedling trays or wash anddisinfect used ones with trisodium phosphate(3 kg /100 litres of water) or other provendisinfectant.

• Tools should be frequently dipped in 150ppm sodium hypochlorite (0.26% householdbleach) plus 0.01% soap; or 5 to 10%trisodium phosphate to reduce the chance oftransmission between plants.

• Workers should use fresh, clean clothes eachday. Use new disposable coveralls or washclothing in hot water and dry in the sun or ina hot dryer.

Tomato Spotted Wilt Virus(TSWV)

Biology and Disease CycleThis virus has a very wide host range, includingmany vegetables, flowers and weeds. It over-winters in perennial flowers and weeds in ornear a greenhouse and can also be introducedto a greenhouse with infected ornamentalcuttings for propagation. Thrips, especiallywestern flower thrips, are required for transmis-sion and spread from plant to plant. Onceinfected thrips remain infected for life.

Disease SymptomsMost plants infected with TSWV are severelydamaged. Growth usually stops after infectionand no marketable crop is produced. Infectedpepper plants show a range of stem, leaf andfruit symptoms. Stems may show lesions withblack margins followed by branch die-back.Leaves often show tan, circular spots withblack margins. Fruits exhibit uneven ripeningand circular blotches of green, orange, yellowand red. The blotches may show ring-spotpatterns. See colour photos 50 & 51.

Management Strategies• Eliminate weeds, ornamentals and thrips

from the greenhouse before bringing in newpepper plants (see Thrips, page 98).

• Maintain a weed-free zone at least 3 m widearound the greenhouse.

• Do not grow ornamentals in the same green-house with peppers or tomatoes. (An excep-tion to this rule is that petunias in hangingbaskets may be used as indicator plants forthe presence of TSWV.)

• Monitor for thrips regularly and keep themunder control.

• Pepper plants exhibiting dwarfing or othersymptoms indicating TSWV should bedestroyed promptly by placing them in asealed garbage bag or other sealed containerand removing them from the greenhouse.


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Physiological Disordersof Sweet Pepper

Blossom-end Rot

This is a very common physiological disorder ofpeppers. It is caused by an interaction of mois-ture shortage within the plant and calcium move-ment to the lower cells of a developing fruit.

Water soaked spots appear at the blossom endwhich enlarge and take on a dark, leatheryappearance. Blossom-end rot may or may notbe associated with external symptoms. Darkinternal tissue and seed can occur with noevidence of external damage. This condition isdifficult to detect on the grading lines. Seecolour photo 52.

Moisture shortages can be caused by a numberof factors:

• under-watering during warm periods;

• high concentrations of fertilizer salt whichimpede uptake of calcium;

• root problems;

• very low humidity levels causing high tran-spiration rates;

• sudden changes in weather from cool to hotperiods can cause moisture stress, affectingcalcium mobility.

Other contributing factors:

• blossom-end rot (BER) occurs during periodsof rapid vegetative growth and rapid fruitexpansion;

• actual calcium deficiency is usually a second-ary factor, since feed should supply adequateamounts;

• some cultivars are sensitive to BER, e.g.Mazurka;

• low pH < 5.5 in the slab especially duringhigh light, fast growing conditions.

Management Strategies• Avoid any of the plant stresses mentioned

above.

• Important to have good balance betweenvegetative/generative before March.

• Ensure Ca:K ratio 6:5.

• pH should not be allowed to drop below pH5.5 in the slab.

• Maintain reasonably high humidity levels inthe afternoon on warm days by restrictingventing, providing it does not increase tem-peratures.

• Ensure soluble salts in the slab are below 2.5EC during conditions that may favour BER.

• Ensure an irrigation capacity of 1.5 to 2 L/m2/hour.

• Fruits with BER should not be removedunless a fruit balance can be maintained.

• Higher ADT tends to favour BER, especiallyduring sunny warm weather.

• Use minimum pipe to stimulate transpiration,especially in early morning (VPD 4 to 7).

• Stimulate transpiration with a minimum pipeespecially in dark weather. High humidityrequires higher pipe temperatures. Thisprocess will condition the plant when higherlight intensities return.

• For VPD 3.0, the pipe required is 50°C; at4.0 VPD, 40°C is adequate

• Keep the temperature down as much aspossible during sunny warm conditions whenfruit set is high. By reducing the tempera-ture, especially at night, high root pressuresare created. This aids calcium transport.

• Avoid use of ammonium during this period(competing ion for calcium uptake).

• Avoid sodium levels more than 6 to 8 mmol/L.


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• Phosphate enhances Ca uptake. Additionalphosphate is usually not required. However,ensuring pH levels in the slab are below pH6.5 (but not below 5.5) will enhance P uptake.

• Stimulate root pressure at night by maintain-ing warmer root temperatures relative to airtemperatures and applying night irrigation.

• During periods of high light and rapid fruitgrowth, keep ADT on the low side by reduc-ing light.

• Weather changes from 200 watts (dark) to1000 watts/m2 (bright), can place stress onthe plant, which is reflected in BER. Useroof sprinklers, 7 to 10 VPD, and screens orshades > 600 watts/m2 to help the plantthrough these transition periods (1 to 3days). Plants having a high percentage ofsmall fruit (less than 2 cm diameters) aresensitive to BER and screens and white washcan be considered.

Sunscald

Sunscald is another physiological disorder thatoccurs commonly on sweet peppers when thefruit is exposed to hot sun. The flesh becomessoft, light-coloured and papery on areas thathad direct sunlight on them. Fruits on plantsadjacent to walkways are more susceptible. Seecolour photo 53.

Management Strategies• Avoid fruit temperatures > 35°C.

• Sensitive-skinned cultivars like orange andyellow are more prone to sun scald.

• Maintain a good leaf canopy or use a sun-screen.

• Apply shading or screening in bright hotweather, > 600 watts/m2

• Prune to 2 – 3 leaves starting in March,especially if fruit size is small.

Shrink Cracks

This condition appears as superficial fine cracksthat develop lengthwise over the fruit surface.These cracks give a corky colour and texture tothe pepper surface (see colour photo 54).Shrink cracks are associated with suddenchanges in the growth rate of the fruits. Thesechanges result in reduced elasticity of the fruitskin that is unable to maintain a balance ofgrowth with fruit development below the skinlayers. Some factors associated with fruitgrowth disruption include:

• periods of dark cold weather;

• imbalances created by the removal of a largepercentage of fruit at one time;

• fruit left on the plant too long has an in-creased probability of having shrink cracks.

Management Strategies• Reduce humidity levels early in the morning.

• Avoid large flushes of fruit; try to maintainmore balance.

• Gradually increase temperatures over severaldays following a prolonged dark or coolperiod to avoid sudden fruit development.

• Lower the temperature of the nutrient solu-tions at night during the ripening phase tohelp reduce root pressure. Increasing rootpressure may aggravate shrink cracking

• Maintain adequate EC in the slab duringfruit ripening.

• Provide adequate leaf cover for fruit insummer.

• Avoid cultivars that appear more susceptibleto this condition.


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Misshapen Fruit (knots)

Fruits affected with this disorder are oftensmall, shorter and contain fewer seeds thannormal fruit. This condition has been associ-ated with low daytime temperatures and lowhumidity during flower set. Plant stress canresult in fewer flowers that tend to be over-sized. These flowers generally do not set easily,resulting in knotted fruit. Differential cultivarsusceptibility to this condition has been ob-served. See colour photo 55.

Management Strategies• Maintain good balance, particularly in the

early stages of growth. Over-harvestinggreen fruit can predispose the plant to mis-shapen fruit.

• Avoid low daytime temperatures (< 20°C),especially during early fruit set.

• Target RH levels as high as 80% during earlyfruit set.

• Remove misshapen fruit in early stages ofdevelopment.

Internal Growths and Wings

Growths that sometime appear as a pepperwithin a pepper can result in wide cracks thatform the length of the pepper. This problem ofabnormal tissue development of the honeygland is associated with the first fruit set ofearly crops. Wings are abnormal growths thatare attached to the shoulders of the fruit. Seecolour photo 56.

Tails

The effect on marketability of this fruit disor-der is not as severe as the previously describeddisorders.Tails result when the style of theflower does not die off in the sequence of fruitdevelopment. A trailing appendage or “tail”develops at the bottom of the fruit. These caneasily break off during handling and may resultin lower grades and shelf life. See colour photo57.

Management Strategies• Fruit disorders tend to be associated with

early fruit set that involves prolonged flower-ing periods.

• Target for optimum flowering and fruit settemperatures and humidity.

• Cultivar differences have been noted withsome of these fruit disorders.

• Growers have reported that physically break-ing off the tail at an early stage will not ad-versely affect the development of the pepperand will improve marketability of the fruit.

Growth Cracks

Growth cracks result from excessive rootpressure, resulting in fruit splitting at an earlystage. This is mainly associated with yellowand orange cultivars. Factors that affect highroot pressure directly affect growth cracks.

Management Strategies• Omit night watering.

• Delay the first irrigation in the morning.

• Increase transpiration in the early morningwith vent temperature above the heatingtemperature (1°C/hour).

• Target EC in slab close to 3.5.

• Avoid slow developing fruit conditions.

Cuticle Cracking

This disorder is similar to shrink cracking;however, the damage is “finer” and appears tobe more of an upper surface blemish. Cuticlecracks have been identified as a key productionproblem impacting the quality of greenhousegrown sweet bell peppers. Cuticle crackingaffects the quality of peppers in three ways:general appearance of the fruit is reduced;there is an increased rate of water loss andwrinkling; and entry points for storage rotorganisms are provided.


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Cuticle cracks are not caused by any singlefactor but appear to be a result of a number offactors combined (e.g. cultivar susceptibility,high VPD at night, high EC, low daytime CO,low yields). Cuticle cracks are associated withsudden changes in the fruit expansion rate.Older fruit, fruit that is on the plant more than8 weeks, and fruit from the last set are morelikely to be affected.

Management Strategies• Provide uniform environment and moisture.

• Lower humidity levels early in the morning.

• Avoid watering too early in the morning.

• Avoid dramatic EC changes, especially aswitch from high to low EC.

• High feed EC is associated with highercuticle cracking in pepper. A feed EC of 2.1– 2.4 mS/cm can lessen cuticle cracking.

• Avoid slow fruit growth speed, maintaining aminimum ADT of 20°C

• Peppers with higher levels of supplementedCO

2 display less severe cuticle cracking.

Supplementary CO2 is recommended with a

target range of 875 – 1100 ppm.

• Avoid low fruit loads.

• Higher average weekly yield is related tolower levels of cuticle cracking. Practicesthat maximize yield are recommended.Target weekly yields in the range of 0.85 –1.06 kg/m2.

• Different varieties display different cuticlecracking susceptibility. As newer varieties areintroduced, the relative susceptibility of thevariety to cuticle cracking should be consid-ered as part of the selection criteria.

Fruit Spots

This condition is associated with small whitedots below the surface of the pepper fruit.These dots are often found on the “shoulders”of the fruit. The condition is associated withexcess calcium levels in the fruit. This resultsin small calcium oxalate crystals forming. Fruitaffected with this condition may have reducedshelf life. See colour photo 58.

Management Strategies• Avoid low fruit loads.

• Conditions that promote high root pressurewill aggravate fruit spotting, e.g. low VPD,low night temperatures, weather changingfrom sunny to dark.


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Greenhouse CleanupGrowers with clean greenhouses have fewer pestproblems. Greenhouse sanitation includes theremoval or exclusion of factors that allow pests togain access to greenhouses, survive from crop tocrop, and spread from plant to plant. Good crophygiene focuses on starting clean and preventingthe introduction of pathogens or insects to thecrop. If possible, growers should empty thegreenhouse entirely between crops and sanitizethe facility. Plants and materials originating off-site should be examined for pests prior to place-ment in the greenhouse. When possible, green-house ventilators and entrances should bescreened against the entry of insect pests. Inaddition, visitor access should be limited andrestricted. See also Greenhouse Cleanup andOther Factors Affecting Insect and Mite Sur-vival, page 78.

Sanitation

Good crop hygiene minimizes the introduction ofpathogens to the crop. Soil-less systems have anadvantage over soil in that the growing mediainitially should not contain any pathogens. Adisadvantage to a soil-less system is that when apathogen invades the ‘sterile’ environment, thereare no antagonistic micro-organisms to suppressits spread.

Restrict access to the greenhouse and wherenecessary, encourage the use of disposable bootsand overalls as insects and disease organisms canbe carried on clothing. Wash clothing frequentlyand especially after working on diseased crops.Regular detergent should be enough to removemost pathogens from clothing.

A foot-bath at the entrance to the greenhouse willhelp prevent the introduction of pathogens onfootwear. Use a foam pad soaked with an appropri-ate disinfectant such as Virkon. Change the solu-tion regularly and ensure that the foot-bath is used.

Pathogens such as Pythium and tobacco mosaicvirus can be spread in water. Water sources suchas rivers and ponds can be contaminated withPythium but city and well water is usually clean.

Do not place cull piles near the source of water.Water tanks must be kept covered to preventcontamination from dust, crop debris, and birds;and to prevent algae growth.

Cull piles are a major source of new infectionseach year. They should be located downwindfrom the greenhouse or removed off-site. Theyshould also be covered with a durable plastic tarpor soil after each deposit to prevent the release ofspores and insects feeding on plant tissue. Work-ers need to wash their hands and footwear ifworking in the crop after making deliveries to thecull pile. However, it is better if they do not workthe crop at all.

When tending the crop, workers should start inthe healthiest part of the crop before moving intoinfected areas. Soak pruning knives in a 10%solution of 5.25% household bleach or a 1.5%solution of Lysol brand disinfectant or it’s equiva-lent, as frequently as possible. A one-minute soakis more effective than a quick dip. Containersfilled with disinfectant can be located at bothends of each row for a knife to soak in while therow is being worked. Three knives per worker arerequired if the knives are changed at the end ofeach row.

Weed Control

Weeds can be a source of mites, aphids, thripsand whiteflies and should be controlled both inand around the greenhouse. Cutting or killingmature weeds around the greenhouse during thegrowing season may cause pests to migrate intothe greenhouse. Plan a weed management strategythat will avoid this. Try to maintain a weed-freezone approximately 5 - 10m wide around thegreenhouse.

Inside the greenhouse, hand-pull weeds andimmediately remove from the greenhouse anduse durable plastic floor mulches to cover thesoil. Do not use herbicides in the greenhouse -residual and breakdown products can be phyto-toxic to plants long after application.

If necessary, use a systemic herbicide such asRoundup (glyphosate) for perennial weeds


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around greenhouse. Annual weeds can becontrolled with a contact weed killer such asGramoxone (paraquat). Either of those herbi-cides may be combined with a residual herbi-cide such as simazine to prevent weed seedgermination for several months. Continued useof such herbicides leads to shifts in weedpopulations so that resistant weed species willeventually predominate. Do not use hormone-type herbicides such as 2,4-D, MCPA or Banvelfor weed control near greenhouses as theyproduce vapours that may enter the green-house. Always apply herbicides at low pres-

sure (less than 275 kPa) to avoid misting

and drift that may be drawn into the green-

house. Do not use herbicides in green-

houses. Do not use the same sprayer for

herbicides and other pesticides. Herbicideuse around the greenhouse during plant produc-tion is not recommended.

Crop Cleanup

The cleanup period at the end of the croppingcycle is an efficient, low cost way to have a freshstart. Careful consideration of each step isimportant during cleanup. A missed step be-comes the weak link in the chain.

General cleanup principles include removingplants promptly from the greenhouse at the endof the crop. Thoroughly cleaning up plantresidues and dispose by burying, burning,composting under cover or hauling away. Avoidstarting new plants in a greenhouse before theold ones are removed. If pests are at a high level,apply a pesticide to the plants in the greenhousebefore removing the old crop. This preventsdispersal of pests during the removal process.

End of Season Preparation BeforeCrop Removal• Inventory diseases and insects within the

greenhouse.

• Ensure the RH in the crop canopy is below85-90%. Adjust your computer settings asneeded.

• Reduce insect populations by late summer. Payspecial attention to spider mites, loopers,aphids and echinothrips. Increase mite preda-tors (Persimilis) from the end of summer to theend of the crop. Consult with an entomologistif you have psyllid, echinothrips or other exoticpests present. Use an insecticide program asearly as possible to reduce insect levels.

• Begin cleanup to reduce pests and diseaseinoculum in early fall. In general, eliminating90% of disease inoculum reduces the inci-dence of disease from 60% down to 10%.

• Continue to remove dead plants promptly.

• Dry down the growing media as you prepareto remove the crop. Reduce the EC asneeded.

• Plan your crop removal strategy. Arrange fordisposal bins if the crop debris is removedoff-site, or excavate a hole that is largeenough to hold the crop debris and thencover debris with soil. Do not pile cropdebris near the greenhouse. If crop remainsare to be composted for use as field fertilizer,the pile should be as far away from thegreenhouse as possible. It must be coveredwith a durable tarp to prevent escape ofinsects, pathogens and environmental con-taminants.

• After crop removal, Dibrom may be used inthe greenhouse. Ensure all vents are closedand the temperature is turned up (20ºC+).This is best done on a sunny day. Dibrom is

not registered for use on peppers and can

only be used after harvest is complete.

See page 87 for use guidelines.

• Keep lines charged at a low rate prior tocleaning to prevent drying out. Once theydry out, it is difficult to remove dried saltsand other debris. After the last harvest, cleanout irrigation lines.

1. Remove EC and pH electrodes.


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2. Divert cleaning solutions away from slowsand filters. Keep the slow sand filterunits charged with old solution.

3. Pressure flush the irrigation lines with airor water before acid or bleach treatment.

4. Flush lines with nitric or phosphoric acidat a pH of 1.6 to 1.7 for 24 hours. This isprepared by adding 1 part 60 to 70% acidconcentrate to 50 parts water. Apply twiceif you have older lines or narrow orificecapillary lines. Caution, some newer

lines, eg. Netafim, have neoprene

diaphragms. These can be damaged

with exposure to solutions with a pH

less than 3.0 or buffered bleach. Con-

sult your supplier for information on

compatible disinfectants.

5. Rinse well; when acid contacts bleach,dangerous chlorine gas may form.

6. Flush lines and tanks with a disinfectant.Buffered bleach has worked well in thepast. There is no data yet on the efficacyof DDAC or hydrogen peroxide for thisapplication although they work well ascontact disinfectants. Hydrogen peroxidecould be used as a trial at 1000 – 3000ppm. Use procedures recommended forbleach but leave the solution in irrigationlines overnight. The efficacy of hydrogenperoxide decreases with the increase inorganic matter in irrigation lines. Hydrogenperoxide is not recommended for use ongreenhouse surfaces or equipment. It ismore effective to flush the lines as a ‘pulsecharge’ four times with one hour intervalsthan to flush with one pulse charge andleave the solution in the line for fourhours. Do not drop the pH of the bufferedbleach solution below 5.0. Target your pHfor 6.5 to 7 and follow all safety recom-mendations on the label. Use a non-phytotoxic surfactant such as Superspredat the rate of 1L/1000 L of water. Usedbuffered bleach solution must be collectedand disposed of in accordance with

environmental guidelines. It can be usedfor other disinfection purposes. It can alsobe de-chlorinated.

7. Rinse with fresh water.

8. Disinfect regular sand filters with bleach.Do not treat slow sand filtration (biologi-cal) systems with bleach.

• When ordering seedlings - specify that thepropagator apply Hypoaspis to seedling blocksfor fungus gnat control. Inspect seedlings atthe propagator house to ensure good planthygiene and health. Insist on new containermaterial for shipment.

• Plan to use foot-baths for the next crop.Order necessary equipment and materials. Acontainer with a foam mat is effective. Usedisinfectants such as Virkon. Change solu-tions regularly.

Cleanup After Crop Removal• Fumigate with Dibrom unless it was already

done prior to crop removal.

• Remove remnants of crop debris from thegreenhouse. Pay special attention to wires,screens, uninsulated pipes and pipe stands.

• Consider steam sterilizing foam androckwool slabs if re-using.

• Soak dripper spikes in acid solution. Rinsewell. Disinfect by soaking in buffered bleach(2000 ppm) for 24 hours.

• Wash tanks with bleach, 1% Virkon orequivalent. Rinse well.

• Power-wash the structure and glass withwater to remove larger pieces of debris.

• Power-wash the structure with a cleaner. Useregistered products and follow label direc-tions. If you have had a virus problem, useVirkon or equivalent. Apply Virkon withLVM or mist when plastic is down. If highlevels of organic debris are present on glassor other surfaces being treated with products


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that work through oxidation such as bleach,DDAC, hydrogen peroxide and Virkon, theirefficacy is significantly reduced. Remove asmuch debris as possible with detergents andwater before applying disinfectants. If using

ammonium bifluoride, remove it within 5

minutes or it will damage glass. Avoid

mixing bleach and ammonia compounds

- hazardous chlorine gas is produced.

• Disinfect totes.

· Disinfect carts/tools/tractor tires, etc. with1% Virkon, DDAC or equivalent. Check thelabel to be sure that the disinfectants will notharm the equipment.

• Use a high pressure wash on the outside ofthe greenhouse. Control weeds around thegreenhouse.

• Remove the old plastic.

• Put new plastic down. Seal the plastic to thewalkways, posts and walls with non-phyto-toxic glue. Some growers are putting hy-drated lime at approximately 15 bags/acreusing a drop fertilizer spreader on the entirefloor before laying plastic. Some are alsousing dormant oil sprays on the soil and atthe base of perlins before laying plastic.

• If painting pipes, be aware that you need afew days of 80-90°C pipe temperatures toproperly dry and volatilize paint, and toprevent phytotoxic fumes from causing injuryto seedlings.

New Crop Establishment• Cover any cull piles with soil or a plastic

tarp. Prepare an area to receive culls from thenext crop. Plan to keep plant debris coveredwith soil or a tarp. Avoid traffic from the cullpile to healthy plants in the greenhouse.

• Meet with staff to discuss pest managementin the new crop. Discuss the importance ofearly pest and disease detection. Explain theearly symptoms caused by specific pests anddiseases.

• If your new plant material originated off-site,check for evidence of pests and diseases

before plants arrive from the propagator.Inspect upon arrival.

• Ensure that trays/carts with propagationmaterial have been bleached before comingto your greenhouse.

• Install a foot-bath. Post signage on use andensure it is being used. Control visitor accessand require them to use disposable coveralls.Insects and disease organisms are carried onclothing.

• Ensure there are no personal ornamental houseplants, etc. in the greenhouse. They may be asource of disease and insect inoculum.

NOTE: Mention of product names does notimply endorsement, and omission does notimply that a product is not effective. Productsmentioned are examples only.

Re-using Growing Media

Although it is always preferable to replace thegrowing media every year, some growers havere-used growing media including sawdust bagsand rockwool. This practice is more viable inpeppers as they are much less susceptible toroot pathogens than cucumbers and tomatoes.This is done primarily for economics and timesaving but it increases the chance of diseasesand may affect how the second crop grows.Steaming rockwool (see below) minimizes thecarry-over of diseases but it is also very labourintensive and requires a very good steamingsystem to be effective.

Experience from Europe suggests that rootsfrom the previous crop make rockwool wetter,which increases the growth in the second cropand can lead to larger fruit sizes. The irrigationmust be adjusted in the second year by startinglater and stopping earlier, and irrigating forlonger periods with longer pauses in between,without changing the actual total volume.Letting the slabs dry out very well at the end ofthe first season can reduce disease carryover solong as the new plants are strong. If the firstcrop had high disease pressure particularly fromvirus or Fusarium, growers should consider


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steam sterilization or using new media bags forthe second crop.

Some growers advise to put the old plants onthe old planting hole even though the firmerarea of the slab can make it harder for the plantto root in. A new planting hole makes moreroom for weeds and the extra hole will bringmore moisture into the greenhouse, whichincreases the chances of Fusarium infections.

There is not much known of the practice of re-using sawdust bags. Some B.C. growers whohave done it, have not noticed significant insector disease carry-over as a result but it is criticalthat the preceding crop is healthy at the end ofthe season. It is not recommended to re-usesawdust media bags if disease or virus pressurewas high at the end of the first crop. In thiscase the risk is far greater than the saving.

Steam Sterilization ofRockwool Slabs*

Steaming rockwool slabs can make economicsense and is environmentally friendly. How-ever, it is important to steam well or yieldscould be reduced. Ensure slabs are as dry aspossible. Drier slabs heat faster than wet slabsso stop watering as soon as the last harvest hasbeen taken. Avoid salt build-up in the slab byincreasing the rate of over-drain two tothree weeks before crop removal. Atthe same time, reduce the EC as muchas possible without affecting cropquality.

Check the physical condition of theslabs and avoid re-using those that havelost greater than 10% of their originalheight. Good quality slabs can be re-used for three years. Slabs can besteamed in situ, stacked on a pallet orsteamed in a container. If done in situ,remove the drip irrigation system if it isnot heat resistant and cover the green-house with polyethylene sheeting. Ifstacking on a pallet, remove the plasticsleeve. Stack slabs no higher than 1.5m

and leave about 2cm between slabs. Stack thesecond layer in the opposite direction of the firstand continue alternating the direction as youbuild each layer. This will give the stack greaterstability. Cover slabs with a sheet and steam.

If the crop had viruses such as tomato mosaicor pepper mild mottle, heat the slabs to 100ºC.Otherwise heat slabs to 75ºC for 20 minutes.Beneficial organisms start to be affected attemperatures above 82ºC. Checking slabtemperatures with a thermocouple is requiredto confirm target temperatures. See Table 5-11.

Steaming slabs in situ takes approximately 10times more energy than when slabs are stacked.Steaming in situ without re-wrapping slabsrequires 310 person hours per ha while stack-ing, re-wrapping and replacing slabs requires560 person hours per ha. Steaming in situ maymaintain the structural characteristics of theslab better than stacking slabs. The problemswith steaming in situ are that it is harder for thesteam to penetrate the sleeves and that if thereare any wet slabs they will not be heated to theappropriate temperatures. These wet slabswould be noticed while handling slabs forstacking and dried out before treatment.

* This information is summarized from D. Runia’s

work at Naaldwijk (1986).

Table 5-11. Time and temperature required to kill various pests and pathogens

Pest or Pathogen Temperature ( C) Time (minutes)

Weeds (most) 70 to 80 15

Insects and mites 60 to 71 20

Bacteria (most) 60 10

Fusarium 57 30

Botrytis 55 5

Nematodes 55 15

Rhizoctonia 52 30

Sclerotinia 50 5

Pythium 46 40


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CROP PROTECTION

This information on safe pesticide use isadapted for greenhouse production from theB.C. Pesticide Applicator Course for Agricul-tural Producers. The course manual is availablefrom Office Products Centre at 1-800-282-7955. Courses and exams are held periodicallythroughout the province. Contact the B.C.Ministry of Water, Land and Air Protection forinformation on scheduled courses.

Canadian Legislation

Pest Control Products Act &Regulations

Every pesticide used or sold in B.C. must beregistered by The Pest Management RegulatoryAgency (PMRA) of Health Canada. Each labelmust have a Pest Control Products Act (PCP)number on it. Using pesticides from othercountries without a Canadian PCP Act # isagainst the law unless you have a “pesticide ownuse import permit”. Besides the PCP #, eachlabel must also list the crops and pests thepesticide can be used on. Pesticides that can beused legally in greenhouses must specify “green-house ”. For example, the pesticide label mustsay greenhouse peppers. Using pesticides foruses not on the label is against the law. How-ever, there are a few minor pesticide uses thatmay be approved but are not on the label. Thisguide includes any of these minor uses that havebeen approved for greenhouse peppers.

Pesticides are labeled as Domestic, Commercialor Restricted. Domestic products are intendedfor home garden use; commercial products arefor agricultural producers; and restricted prod-ucts are more hazardous and are intended foruse only by certified pesticide applicators.

The Food and Drugs Act

All foods must be free of harmful amounts offoreign substances. Health Canada sets levelsof allowable pesticide residues on crops atharvest. These levels are called maximumresidue limits or MRLs. Foods are tested peri-odically for pesticide residues at the time ofsale. If residues are found to exceed the MRLfor any pesticide on that crop, the food may beseized. If you follow the recommendations onthe label or in this production guide, make nomistakes in calculations, and wait the requireddays after application before harvest, residuesshould not exceed the MRL.

The Fisheries Act andMigratory Birds RegulationsYou can be charged if you kill or harm fish ormigratory birds with pesticides. This applies tocreeks, rivers, and lakes on your own propertyas well as on public land. It is illegal to intro-duce pesticides into waters either directly orindirectly through spray drift or run-off.

Transportation of DangerousGoods Act

Certain dangerous goods cannot be transportedunless you use shipping documents, speciallabels, and vehicle signs. Ask your pesticidedealer if the product you have bought needsspecial transport procedures. Growers areusually exempt from this when they are trans-porting less than 500 kg of pesticide.


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British ColumbiaLegislation

Pesticide Control Act andRegulations

The Ministry of Water, Land and Air Protection hasrules about the sale and use of pesticides in B.C.

1. Pesticides labeled Restricted or Commercialmust be kept in vented and locked storagewhich has a warning sign on the door.

2. Anyone buying or using pesticides labeledRestricted must have a current pesticideapplicator certificate.

3. Businesses selling pesticides must be licensedand their sales people must include at leastone certified pesticide dispenser on duty.

4. Anyone applying pesticides in exchange for afee must have an applicator certificate and aPest Control Service License. But, if you sprayyour neighbor’s crops as a favour and no moneyis exchanged, you do not need a license.

5. Everyone must dispose of containers andleft over pesticides safely.

Workers’ Compensation Board

Workers’ Compensation Board (WCB) Regula-tions for Occupational Health and Safety inAgriculture apply to farmers who are registeredor are required to be registered by WCB. If youare unsure whether they apply to you, call WCBat 1-800-661-2112.

The WCB regulations cover conditions ofworkplaces such as general safety procedures;hazardous substances including pesticides;confined spaces such as tanks and bins; protec-tive clothing; and maintenance and operationof equipment, tools, and machinery.

The WCB regulations on pesticides outlinerequirements for pesticide applicator certifica-tion, emergency medical care, washing facili-ties, personal protective clothing and equip-ment, application equipment, pesticide applica-tion, posting warning signs, re-entry into treatedareas, and record keeping. Free copies of theregulations are available from any WCB office.

One of the WCB pesticide regulations statesthat workers must be over 16 years old andmust have a valid pesticide applicator certifi-cate if they mix, load or apply moderately orvery toxic pesticides or if they clean or main-tain application equipment for these pesticides.The relative toxicity table in this guide indi-cates which pesticides are classified as moder-ately or very toxic (see Table 7-1).

The WCB worker re-entry requirements aregenerally 48 hours for highly toxic chemicalsand 24 hours for moderately toxic chemicals.Chemicals rated as slightly or non-toxic mayhave shorter or no waiting periods prior to re-entry. Refer to the WCB regulations for moreinformation.


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Trade names are capitalized; common names are in lower case. Toxicity data are based primarily on tests with rabbits and rats and are considered relevant to all mammals, including humans. The original source of information for this table was “Farm Chemicals Handbook” 1993, Sine, C. ed., Meister Pub. Co. Data for more recent registrations is from the 1999 edition of the same publication and other sources. The following categories have been used to differentiate toxicity ( LD50 is defined as the quantity of active ingredient in mg that must be fed per kg of test animal body weight to kill 50% of the population of animals in the test) : Toxicity Rating Oral LD50 Dermal LD50

slight 500 + 1000 + moderate 51 – 500 201 – 1000 very 0 – 50 0 – 200 The chemical or mode-of-action class category is of value in determining rotations to avoid build-up of pest resistance. It is also of value in planning precautions taken to limit worker exposure. For example, all OP compounds are cholinesterase inhibitors and exposure is cumulative regardless of the number of different OP products being used. Following is the key to chemical class designations: Code Chemical or Mode-of-Action Class Code Chemical or Mode-of -Action Class BI biological I inorganic BOT botanical MO miscellaneous organic C carbamate OC organochlorine CN chloronicotinyl OP organophosphate D dithiocarbamate PP phosphonic acids MAC moult accelerating compound SI sterol inhibitor The requirement for applicator certification in commercial operations differs between BC Ministry of Water, Land and Air Protection - Pesticide Control Act regulations and BC Workers’ Compensation Board regulations. In the following table, “yes”, means certification is required; “no”, means it is not required.

Table 7-1 List of pesticide common names, trade names andrelative toxicity to mammals.


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Table 7-1 (Continued) List of pesticide common names, trade names and relative toxicity to mammals.

Common Name

Trade Name(s) Class Oral Toxicity

Dermal Toxicity

WLAP Regs

WCB Regs

Fungicides captan Captan, Maestro OC slight slight* no no myclobutanil Nova SI slight slight no no oxine benzoate

No Damp MO slight slight no no

Streptomyces griseoviridis

Mycostop BI slight slight* no no

sulphur Microscopic Sulphur I slight slight no no thiram Thiram C slight slight** no no Herbicides glyphosate Roundup PP slight slight no no paraquat Gramoxone MO moderatet moderate no yes Insecticides and Miticides

abamectin Avid, Agrimeck BI moderate slight no no Bacillus thuringiensis

Dipel, Foray, Vectobac BI slight slight no no

diazinon Basudin, Diazinon OP moderate slight no yes endosulfan Thiodan OC very moderate no yes imidacloprid Merit, Intercept CN moderate slight no yes mineral oil Dormant Oil MO slight slight no no naled Dibrom OP moderate slight no yes nicotine Plantfume Nicotine BOT veryt very yes yes pyrethrin (with soap in) Trounce BOT slight slight no no pyridaben Dyno-mite, Sanmite MO slight slight no no soap Safer’s Insecticidal Soap MO slight slight no no tebufenozide Confirm MAC slight slight no no Molluscicides ferric phosphate

Sluggo Slug bait I slight slight no no

metaldehyde Slug-em Slug Bait MO slight moderate no no Rodenticides zinc phosphide

Phosbait, Rodent Pellets I very slight yes yes

all others various MO very various no yes * may cause allergic reactions; ** do not consume alcohol before or after use; t do not inhale spray or smoke particles.


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ToxicitySome pesticides are more poisonous or toxic thanothers. Pesticides listed in this guide are ratedaccording to their acute toxicity in Table 7-1.

Hazard Shapes and Symbols

Hazard shapes and symbols on pesticide labelsindicate how dangerous a pesticide may be. Theshape indicates how hazardous the product is.The symbol inside the shape tells you the typeof hazard. If there are no shapes and symbolson the label, the pesticide has very low hazard.See Pesticide Warning Symbols, Figure 7.

Exposure

Pesticides can enter your body through the skin(dermally), the mouth (orally), the nose (inhala-tion), or the eyes. The skin is the most commonroute of poisoning for pesticide applicators.Skin contact may occur from a splash, spill ordrift. Your skin is most likely to get contami-nated when mixing and loading pesticides.

Hazard

The hazard of using a pesticide depends onboth its toxicity and the amount of exposure.Reduce hazards by selecting pesticides with lowtoxicity when possible and by reducing expo-sure. Wear protective clothing and follow safehandling procedures.

Poisoning and First Aid

Symptoms of PesticidePoisoning

Know the poisoning symptoms of the pesti-cides and other hazardous chemicals you areusing. Read pesticide labels for symptoms.Effects from pesticide poisoning vary fromperson to person and are often difficult torecognize. Some poisoning symptoms areheadache, tiredness, nausea, dizziness, irritationof the skin or nose or throat, blurred vision,tiny pupils, trembling, perspiration, difficultbreathing, vomiting, and unconsciousness. Callthe Poison Control Centre immediately if you

suspect poisoning (Lower Mainland of B.C.:

604-682-5050, 604-682-2344; elsewhere inB.C.: 1-800-567-8911). Have the common andtrade names and PCP # of the pesticide orname of hazardous chemical at hand when youcall. Follow their instructions; if advised to callfor an ambulance, dial 911 in areas whereavailable.

Poison Control Centre

The Poison Control Centre has trained staff onduty 24 hours a day. They give first aid infor-mation and treatments for poisoning. You musthave the name of the suspected chemical orpesticide available when you call.

The phone number for the Poison ControlCentre is near the front of your phone bookunder Emergency Numbers. The phone num-bers in July, 2004 were those shown at the topof this page.

First Aid

Make sure that at least one person on dutyknows what to do in case of an emergency.Large greenhouses should have a first aid roomwith one or more staff members with first aidtraining available on call.

If someone appears to be the victim of chemicalpoisoning:

1. Protect yourself.

2. Move the victim from the area of contamination.

3. Check if the victim is breathing. If breathinghas stopped or is very weak, clear the airwayand begin artificial respiration. Continueuntil the victim is breathing normally or untilmedical help arrives. When doing mouth-to-mouth resuscitation, use a plastic mask toprotect yourself from poison.

4. Call the Poison Control Centre, doctor orambulance. Be ready to give them the nameof the chemical or pesticide and it’s PCP #.If you have a clean copy of the pesticidelabel, offer it to the ambulance attendantswhen they arrive.


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• very poisonous

• (oral LD50

less than 500)

• wear a respirator

• wear eye protection

MOST POISONOUS LESS POISONOUS

DANGER POISON WARNING POISON CAUTION POISON

MOST FLAMMABLE LESS FLAMMABLE

DANGER WARNING CAUTION

EXTREMELY FLAMMABLE FLAMMABLE

FLAMMABLE

MOST CORROSIVE LESS CORROSIVE

DANGER WARNING CAUTION

EXTREMELY CORROSIVE CORROSIVE

• moderately poisonous

• (oral LD50

500 to 1000)

• wear a respirator in

confined spaces

• wear eye protection

• slightly poisonous

• (oral LD50

1000 to 2500)

• wear a respirator in confined spaces

• could be an eye irritant, eye protec-

tion advisable

→

→

→

Figure 7-1. Pesticide warning symbols and shapes on chemical labels

show the hazards of the product.

(NOTE: the LD50 scale is not the same as the one in Table 7-1.)


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5. Unless the doctor or Poison Control Centretells you otherwise, follow the procedureslisted below:

If a pesticide contacts the eyes, put on water-proof gloves and hold the eyelids open andrinse with clean water for 15 minutes or more.Do not use an eye-cup.

If pesticide contacts the skin, put on water-proof gloves, remove the contaminated cloth-ing, and wash the affected area of the skin withlots of soap and water.

If pesticide was inhaled, take the victim tofresh air as quickly as possible; loosen tightclothing and watch for signs of unconscious-ness or convulsions. Keep the airway open andbegin resuscitation if breathing has stopped oris difficult. Use a plastic face-mask to protectyourself.

If a pesticide is swallowed, check the label tosee if vomiting is recommended. Do notinduce vomiting if:

• the label says not to,

• the substance swallowed contains a petro-leum product,

• the victim is unconscious or convulsing, or

• if the substance is corrosive, such as concen-trated acid or alkali.

To induce vomiting, give the victim water andtickle the back of the throat and tongue withyour finger. If the victim cannot sit, place theperson face down on their side. Keep theairway free of vomitus.

If a corrosive substance was swallowed and thevictim is conscious and able to swallow, give ahalf to full glass of milk or water. Do not givelarge amounts to drink as it may induce vomit-ing. Do not induce vomiting if a petroleum

product, strong acid or strong alkali has

been swallowed.

Protective Clothing andEquipmentWear protective clothing and equipment tominimize exposure to pesticides. Wear safetyequipment during mixing, loading, application,and cleanup. Always wear coveralls, waterproofboots, waterproof gloves, and waterproof hat.Sometimes you will need to wear eye or faceprotection, respirator, waterproof apron, water-proof pants and jacket. The equipment you needdepends on the toxicity of the pesticide andmethod of application. Follow the safety recom-mendations on the pesticide label.

Coveralls

Wear long sleeved coveralls over full-lengthpants and long-sleeved shirts. Make sure thecoveralls are closed at the neckline and wrists.Remove your coveralls as soon as you havefinished your pesticide activities. Remove themimmediately if they become wet through withpesticide. Wear waterproof clothing if youmight get wet during pesticide application.

Some disposable coveralls are suitable forpesticide use. Check with your supplier to seewhich ones can be used for pesticide applica-tion. When removing disposable coveralls, takecare not to contaminate the inside if you planto wear them again. Between wearing, hangthem in a well- ventilated area away from otherclothing. Do not launder disposable coverallsbut do wash clothing worn under disposablecoveralls as you would other clothing wornduring pesticide use. Replace with a newcoverall when severe pilling (balls on the sur-face), rips or holes appear. To discard, place ina plastic garbage bag and take to a landfill site.Do not burn.

Gloves

Always wear gloves when handling pesticides.Many glove materials are available. Use unlinednitrile gloves unless the pesticide label recom-mends a different material. Do not use glovesmade of leather, cloth, or natural rubber or


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gloves with cloth linings. Make sure the glovesdo not have holes or leaks. Keep your coverallsleeves over the gloves and fold down the topsof the gloves to make cuffs. Wash your glovesbefore removing them and after each use.

Boots

Wear waterproof, unlined knee-high boots ofrubber or neoprene when you load, mix orapply pesticides. Wear your pant legs outsideof your boots. Do not wear boots made ofleather or fabric. Wash the outside of yourboots after each use.

Goggles and Face Shields

Wear goggles if there is a chance of gettingpesticide spray or dust in your eyes. Do not usegoggles with cloth or foam headbands. Do notwear contact lenses when handling pesticides.Face shields provide extra protection whenmixing and loading toxic pesticides. Washgoggles and face shields after use.

Hats

Wear a waterproof hat when pesticides may besplashed or when you could be exposed to drift.Wear a wide brimmed rubber rain hat if youmay get wet with spray. Do not wear baseballcaps, fabric hats, or hats with leather or clothinner bands.

Aprons

Waterproof aprons provide convenient protec-tion while mixing and pouring concentratedpesticides.

Respirators

Wear a respirator when the label says to wearone; or when the label says to avoid inhalationof dust, vapour, or spray mist; or if there is adanger poison symbol on the label; or if you areapplying pesticides in an enclosed space. Makesure your respirator fits. Men with beards mayhave difficulty with some types of respirator asfacial hair prevents a proper fit.

Full-face respirators or ‘space helmets’ givemore protection and may be more comfortablethan a half-face mask and goggles.

Do not use dust masks when applying sprays.They do not protect you from the fumes.

Special respirators must be worn when using ahighly toxic fumigant such as methyl bromideor nicotine smoke. Check the label for details.

Respirators must be approved by NIOSH or anagency sanctioned by the Workers’ Compensa-tion Board. The cartridges remove toxic fumesfrom the air. Cartridges labeled for organicvapors or pesticides are needed for most pesti-cides. Filters remove dust and mist. Bothfilters and cartridges must be replaced regularlyfor the respirator to work.

When you use your respirator:

1. Check the intake and exhaust valves.

2. Make sure there are no air leaks around theface-mask. Do an inhalation or exhalation test.

3. Change the dust filter after 4 hours of use ormore often if breathing becomes difficult.

4. Change the cartridges after 8 hours of use orsooner if you can smell the pesticide. Re-place cartridges at least once per year; moreoften if you use them frequently.

Store your respirator in a clean sealed plasticbag.

Protective Equipment forFumigants, Smoke Bombs andFoggers

Use a full-face gas mask with correct canisterwhen applying very toxic pesticides indoors.Keep a fresh canister on hand as they can losetheir effectiveness.

Wear a full-face mask when lighting smokebombs and when airing the house. Light thebomb farthest from the door and work towardthe door. If smoke bombs are placed in more


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than one path, they should be ignited simulta-neously by a separate person in each path.

When using fogging machines, wear completeprotective clothing, including hat, jacket, pantsor coveralls, rubber gloves, and an air-tight,full-face mask.

Cleaning Protective Clothingand Equipment

After application wash your gloves, boots,goggles, face-shield and apron. Wash yourrespirator face piece with soap and warm water.Then rinse it with clean water and dry it with aclean cloth. Keep the cleaned respirator in aplastic bag in a clean, dry place. Store therespirator and protective clothing away frompesticides and spray equipment.

Discard disposable coveralls or any clothingthat has become soaked with a pesticide.

Launder all your clothing after each day ofapplying pesticides. Wash protective clothingseparately from the rest of the laundry. Use ahigh water level and the hottest water settingon your machine. Run through an extra rinsecycle.

If clothes are heavily contaminated, run twocomplete cycles and then clean the washingmachine by running it through a full cycle withdetergent and no clothes to remove any pesti-cide residue. Hang clothes outside to dry in thesunlight if possible.

Personal and

Environmental SafetyGuidelines

Buying Pesticides

• Make sure the pesticide is registered for yourspecific use.

• If possible, buy only what you can use up inone growing season.

Transporting Pesticides

• Never transport pesticides with food, feed,clothing, or household goods.

• Lock up the pesticides if you leave yourvehicle.

• Never transport pesticides in the passengersection of a vehicle.

• Ask the supplier if you need shipping papersand hazard warning signs.

Storing Pesticides & Shelf Life

Pesticides vary in their stability and response tostorage conditions. Try to purchase only quan-tities of pesticides that can be used up in onegrowing season. However, under good storageconditions, most pesticides can be used after atleast one year of storage. Follow these guide-lines for storage:

• Commercial and Restricted pesticides mustbe kept in locked and vented storage that hasa warning sign on the door.

• Store pesticides in the original container withthe original label.

• Never keep pesticides near livestock, food,feed, seed, fertilizer, wells, water supplies,drainage ditches or in your home.

• Keep herbicides separate from other pesti-cides to avoid cross-contamination.

• Keep all pesticides, including herbicideslocked up to prevent theft and/or vandalism.(One container of herbicide could wipe outan entire greenhouse crop.)

• Keep a current inventory of the pesticides instorage so you will know if anything ismissing.

• Protect the pesticides from extreme tempera-tures. Some liquid pesticides are destroyedby freezing; others volatilize when too warm.

• Keep containers securely closed.

• Do not store fertilizer with pesticides as itmay become contaminated by absorbingpesticide vapours.


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• Do not store any feed, seed or slug bait(except in rodent-proof containers) withpesticides as they may attract rodents thatwill proceed to damage the pesticide contain-ers and labels.

• Dispose of unwanted, unmarked and dam-aged containers when a free disposal day isoffered. These are provided periodically.Contact your supplier for details.

• Keep containers above floor level to protectfrom dampness and flooding.

• Post emergency numbers near-by.

• Keep a fire extinguisher, broom, shovel,absorptive material, and protective clothingnear-by in case of a fire or spill.

Mixing and Loading Pesticides

• Wear protective clothing and equipment.

• Read and follow label directions.

• Choose a mixing and loading site away frompeople, livestock, pets, wells, drains andwater bodies.

• Measure accurately.

• Hold the container below eye level whenmeasuring or adding pesticide into the spraytank.

• Use measuring and mixing equipment re-served for pesticides and return to lockedstorage when not in use. Preferably markthem with durable “for pesticides only”.

• Rinse pesticide containers as soon as they areempty. Rinse measuring and mixing equip-ment. Put rinse water into the spray tankduring the last filling.

• Use potable water of pH 5.0 to 7.0 for allspraying if possible.

• Prevent overflow. Never leave the tankunattended once the pesticide has beenadded to the water.

• Prevent contaminating the water supply byleaving at least a 15 cm air gap between theend of the filler hose and the water in the

spray tank. Alternatively, you can use aback-flow prevention valve on the watersupply but it must be checked annually by aqualified technician.

Applying Pesticides

• Read and follow label directions.

• Use calibrated application equipment.

• Use the label or production guide rate.

• After applying pesticides, wash hands andface before eating, drinking, smoking, orusing the toilet.

• Have fresh water and emergency supplies onhand in case you spill pesticide on yourself.

• Make sure the area to be treated is clear ofpeople and animals.

• Don’t work alone when handling very toxicpesticides.

• Post warning signs if necessary to keeppeople out of treated areas.

• Use separate equipment for applying herbicides.

• Cover or remove animal food and watercontainers near the treatment area.

• Wear gloves to replace or clean pluggednozzles. Do not blow out a plugged nozzleor screen with your mouth. Use a soft brushor toothpick.

After Applying Pesticides

• Clean equipment away from water suppliesand drains.

• Remove and clean protective clothing andequipment.

• Keep records of every application. Preferably,keep one copy near the pesticide storage areaand one copy in the greenhouse office. Severalgrowers have reported misplaced or vandal-ized spray records. A paper original withfrequent computer backup is ideal.


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Disposal of UnwantedPesticides

• Calculate the amount needed so none is leftover.

• Do not re-spray an area to get rid of left-overspray.

• Apply left-over material according to labeldirections on another site or crop listed onthe label. Do not put unwanted pesticidesinto sewers, down drains, or on the land.

• Contact your supplier for information on thedisposal of unwanted pesticides. Free dis-posal days are offered periodically.

• While waiting for a free disposal time, placecontainers of unwanted pesticides in asuitable size drum marked “pesticides fordisposal only” Keep the drum locked awayin your pesticide storage until you can dis-pose of it.

Disposal of Containers

• Triple or pressure rinse emptied drums, glassbottles, plastic and metal containers into thespray tank. Rinse plastic and paper bags onceor twice by holding the neck closed andshaking back and forth before emptying intothe tank.

• Empty all rinse water into the spray tank.The amount of pesticide added to a largetank will not be significant compared to theamount added by measurement. For a smallspray tank, estimate the amount of pesticidein the rinse water and reduce your measuredamount accordingly.

• Crush, puncture or damage empty containersso they cannot be re-used. A limited numberof cleaned and flattened containers can beincluded with the regular waste removal.

• For larger numbers of containers, contactyour supplier to find out where and whenthey can be returned. It is not necessary todestroy containers being returned to thesupplier but they do have to be completelyrinsed out.

• Do not attempt to burn unwanted pesticidesor empty pesticide containers. Dangerousfumes will be produced.

Re-entry Restrictions

Poisoning may occur when people work intreated areas too soon after pesticides havebeen used. Such poisoning may be from breath-ing pesticide fumes or handling treated plantswhen tying, pruning and picking. Even pesti-cides of low toxicity may cause discomfort,especially for workers subject to allergies.

If a person needs to enter a treated area beforethe re-entry period is over, protective gear mustbe worn.

Harvesting Restrictions

Wait the pre-harvest interval (days-to-harvest)before picking to avoid illegal pesticide residueson harvested produce. Maximum residue limits(MRLs) for greenhouse peppers assume that theconsumer receives and consumes unwashedfruit. Pre-harvest intervals can be found on thepesticide labels and are also listed for eachrecommendation in this publication.


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Special EnvironmentalPrecautions

Protecting Fish and OtherWildlife

All insecticides, as well as some fungicides andherbicides, are very toxic to fish. Insecticides aretoxic to birds and wildlife. Exposure to traceamounts of these pesticides may kill fish orbirds. Removing vegetation along fish-bearingwater harms fish by removing food and shelter.

Protect fish and wildlife from pesticide poison-ing by following label precautions and theguidelines below.

• Use pesticides only when necessary.

• Select the least toxic and least persistentpesticides for the purpose.

• Leave a buffer zone along all bodies ofwater, including drainage ditches, to keeppesticides out of the water.

• Use precautions to prevent drift, leachingand run-off to areas outside the treated area.

• Growers not equipped to re-circulate drain-age water must be particularly vigilant aboutthe quality of water leaving the greenhouse.

• If rodent baits are used outside the green-house, they must be placed in secure, cov-ered bait stations to prevent poisoning oflarger animals.

Protecting Bees and BeneficialInsects

Bees and other pollinating insects are essentialfor the production of many crops. Beneficialpredators and parasites are essential to green-house biological control. Many pesticides,particularly insecticides, are very toxic tohoneybees, wild bees, and beneficials. Growersusing beneficials in IPM programs must be veryselective in the choice and timing of chemical

pesticide applications. Populations ofbeneficials provided by different suppliers maydiffer in tolerance to some pesticides. There-fore, it is essential to obtain information fromyour own supplier before using pesticides in acrop using biocontrol.

Emergency Response

• Keep the phone numbers for local PoisonControl Centre, doctor, ambulance (911 inheavily populated areas), and ProvincialEmergency Centre (1-800-663-3456) nearby.

• Have protective gear and equipment easilyavailable.

• Keep absorptive material, a container forcontaminated waste, tools to pick up con-taminated material, bleach, and hydratedlime available.

Spills• Protect yourself.

• Keep bystanders away.

• Contain the spill. Surround and cover withabsorbent material.

• Put absorbent material in special wastecontainer and seal it.

• Remove and wash protective gear. Shower.

• If you need help and for large spills, call theProvincial Emergency number,1-800-663-3456.

Fires• Let your fire department know ahead of time

where you store your pesticides and otherhazardous chemicals.

• Call the fire department and keep peopleaway from the area. Advise firefighters ifpesticides or other toxic chemicals are storednear the burning area.


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Properties of Chemicaland Biological CropProtection ProductsThis chapter is intended for reference andbackground information only; it is by no meansintended to replace labels. Always consult thelabel; it is the primary source for informationon safety, rates, and application methods.Material in this chapter was compiled from thefollowing sources: Farm Chemicals Handbook ’99,MeisterPro Reference Guides; pesticide labels;The Pesticide Manual, Eleventh Edition, EditorC. D. S. Tomlin, British Crop Protection Coun-cil, 1997; and the Handbook for Pesticide Applica-

tors and Dispensers by B.C. Ministry of Water,Land and Air Protection.

Fungicides and Bactericides

captan (Captan, Maestro)Captan is a broad-spectrum, protective andcurative dicarboximide that controls seed andsoil-borne diseases. It may be used as a soiland greenhouse bench treatment for damping-off and root rot diseases of seedlings andtransplants. Do not combine with oil orstrongly alkaline materials such as hydratedlime. Do not use in combination with, imme-diately before or closely following an oil spray.It has low mammalian acute toxicity (LD

50:

oral = 9,000), but it may cause skin and eyeirritation. It is toxic to fish.

myclobutanil (Nova 40W)Nova is a sterol-inhibiting product for pow-dery mildew that is locally systemic and hasboth eradicant and protectant properties. Itis important not to exceed the maximum ofthree applications per growing season or touse higher than label rates. For greenhousepeppers, it should be applied at first sign ofmildew and again 12 days later. It has a 3day PHI and 12 hour re-entry on greenhousepeppers. Note the phytotoxicity disclaimeron the label. In the United States,myclobutanil labels carry the warning that

over-dosage can result in observable foliargreening and shortened internodes. Use extracaution during cool, dark periods when plantsare not growing rapidly. It has low mamma-lian acute toxicity (LD

50: oral = 1,600; dermal

> 5,000), but is hazardous to fish.

Streptomyces griseoviridis strain k61(Mycostop)

Mycostop is a biofungicide for the control orsuppression of damping-off, root and stemrot and wilt caused by Fusarium of green-house tomato, cucumber and pepper. It islabeled for seed treatment and as a drenchalthough seed treatments are not recom-mended for sweet pepper. It is a preventivetreatment; it is not a quick fix or curativetreatment. It must be applied to the growingmedia of plants during propagation and/orimmediately after transplanting. For green-house peppers in rockwool blocks, it shouldbe applied immediately after transplantingand at 3-6 week intervals. Do not tank mixwith chemical pesticides or strong fertilizers.

It is a living organism and cannot be treated thesame as conventional fungicides. Storageconditions, soil and air temperatures, and the useof other pesticides or fertilizers can affect itsperformance. Unopened packages must bestored in a cool dry place where temperatures arebelow 8ºC. Once packages are opened theproduct must be used the same day since theproduct will lose its activity. It will not workproperly unless basic disease strategies such assanitation and proper growing conditions arefollowed. Use well-drained media; do not subjectcrops to water stress; keep greenhouse humiditybelow 85%; and ensure that pH and nutrientsare within the proper range for each crop.

Mycostop contains naturally occurring soilbacteria and suppresses disease throughseveral ways. It deprives pathogen fungi ofliving space and nourishment by colonizingplant roots in advance of fungi. In addition,it secretes various enzymes and metabolitesthat inhibit pathogen growth. It has been


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shown to promote the growth and yield ofplants even in healthy crops.

It has low mammalian acute toxicity (LD50

:oral > 9,000), but may cause an allergic skinreaction. It is toxic to fish. It is believed tobe compatible with most beneficials.

sulphur (Bartlett Microscopic)Sulphur is a naturally occurring element thathas been used to control plant diseases,especially powdery mildew, since ancienttimes even before the cause of disease wasunderstood. It may injure plants during hot,dry weather. Do not tank-mix or use incombination with, immediately before orimmediately after an oil spray. Do not usewhen temperatures are above 30ºC. It isrelatively nontoxic to humans, but may beirritating to the eyes and skin. It is alsorelatively nontoxic to animals and bees. Forgreenhouse peppers, do not apply more than10 applications per crop cycle or more fre-quently than every 14 days. It currently has a24 hour re-entry period.

thiram (Thiram Seed Protectant)Thiram is not applied to greenhouse cropsbut it is used as an alternate to captan fortreatment of vegetable seed against damp-ing-off and some seed-borne pathogens.Workers in seedling production facilities whoare exposed to thiram-treated seed for pro-longed periods should avoid consumingalcohol immediately before or for 24 hoursafter exposure.

Insecticides and Miticides

abamectin (Avid)Avid is a naturally derived miticide/insecti-cide produced by the soil microorganismStreptomyces avermitilis. It acts by stimulatingthe presynaptic release of GABA, an inhibi-tory neurotransmitter. Pests become immobi-lized shortly after ingesting or coming incontact with it. It may take three to four daysto achieve maximum mortality; pests willcontinue moving, but will not feed or breed.It has translaminar activity and penetratesthe leaf tissue and remains there, so whenit’s applied to upper leaf surfaces, it pen-etrates into tissue and kills pests that inhabitand feed on lower leaf surfaces. Surfaceresidues rapidly dissipate and degrade insunlight.

On greenhouse peppers, it is used for controlof two-spotted spider mites. It is effectiveagainst all mite stages except the egg stage; itis effective against leafminer larvae andadults. It has moderate mammalian acutetoxicity (LD

50: oral = 300; dermal > 1,800).

It causes substantial, but temporary eyeinjury. It is toxic to predatory mites, fish,wildlife, and highly toxic to bees.

Effectiveness is limited to between Februaryand October and/or when daily light inten-sity in the greenhouse is at levels higher than700 joules/cm2/day. Apply when spidermites first appear and repeat as necessary tomaintain control. For resistance managementpurposes, it is recommended not to use it insuccessive applications. Rotate sprays withat least one other product before using itagain. Do not apply more than twice insequence or more than five times per crop.Do not apply within 3 days of harvest.


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Bacillus thuringiensis (Foray 48BA,Vectobac 600L, Safer’s BTK)

BT is a microbial insecticide based on toxinsproduced by a bacterium. There are anumber of varieties of this bacterium thatare toxic to specific groups of insects. Thetwo main varieties used in commercialproducts are Bacillus thuringiensis var. kurstaki,

used to kill leaf-eating caterpillars and B.

thuringiensis var. israeliensis, used to kill fungusgnat larvae. Products are formulated as awettable powder, dust, or liquid suspensionof spores and crystals produced by thebacteria. They must be eaten by the targetinsects to cause toxic effects; there is nocontact activity. Thorough coverage is essen-tial. The pest stops all further eating anddeath occurs within one to three days. It hasa short residual effect, so applications mustbe repeated every few days until control isachieved. Products do not control the adultstage life cycle, so they must be applied forwhen the target pest is in the correct stage ofits life cycle. There is evidence for resistancebuilding in greenhouse looper populations soproper resistance management is important(i.e. avoid doses below the label rate, ensurethorough coverage and use alternative con-trols). Avoid applying in conjunction withfertilizers or fungicides that contain copperor chlorine because they may neutralize theactive ingredient. Do not apply to plantsunder stress or follow application withexcessive amounts of water. It has a lowmammalian acute toxicity (LD50: oral =5,000 - 13,000; dermal = 75,000).

diazinon (Diazinon 500E)Diazinon is a broad-spectrum organophos-phate compound that is non-systemic withcontact, stomach, and respiratory action. Ithas moderate residual activity. Phytotoxic tosome plants. Emulsifiable concentrates maycause more plant damage than wettablepowders It has moderate mammalian acutetoxicity (LD

50: oral = 300 - 400; dermal =

3,600). It is toxic to fish, bees (highly), birds,

and wildlife. Aplications may be mademonthly or when aphids reach treatmentlevels. Pre-harvest interval (PHI or days-to-harvest) is 5 days for peppers.

endosulfan (Endosulfan, Thiodan40EC)

Thiodan is an organochlorine compound thatis non-systemic with contact and stomachaction. It is fairly persistent, undergoes slowhydrolysis, and is stable in sunlight. This

product should only be used as a last

resort as it is incompatible with most

biocontrol programs. It has high mamma-lian acute toxicity (LD

50: oral = 22.7 - 160;

dermal = 359) and is very toxic to fish andmoderately toxic to bees and birds. Foraphids and tarnished plant bugs on green-house peppers, it may be used up to twiceper season. PHI is 2 days.

imidacloprid (Intercept 60WP)Intercept is a chloronicotinyl that combinessystemic activity with long residual controlof aphids and whiteflies. It has no effect onspider mites. It is not used as a foliar spraybut as a soil drench to actively growingplants with established root systems. It istranslocated upwards in the plant. Usecalibrated drip, hand-held or motorizedirrigation equipment to apply the soil drench.For best results, do not leach media for 10-14 days after application. It is harmful toAphidius and Aphidoletes. Effect on otherbeneficials is unknown. It has moderateacute mammalian toxicity (LD

50: oral = 450;

dermal = >5000. It is highly toxic to aquaticinvertebrates. PHI is 3 days.

naled (Dibrom)Dibrom is a fast acting broad-spectrumorganophosphate fumigant formed by theaction of bromine on dichlorvos. It is non-systemic, with contact and stomach action,and it provides some short residual fumigantaction. Dibrom is not registered and

cannot be used on greenhouse peppers,


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but can be used for end-of-season

cleanup in empty greenhouses. It has amoderate mammalian acute toxicity (LD

50:

oral = 272 - 376; dermal = 1100). It iscorrosive; causing irreversible eye and skindamage. Dibrom is toxic to fish and highlytoxic to bees.

nicotine (Plant-fume Nicotine SmokeFumigator)

Nicotine as the alkaloid or sulphate is a by-product of tobacco that is used as a fumigantfor greenhouse crops. It may be used tocontrol aphids and thrips on greenhousepeppers. It is non-systemic, with predomi-nantly respiratory action, but it also hasslight contact and stomach action. It can bephytotoxic to tender plants. Preharvestinterval (PHI or days-to-harvest) for peppersis 5 days and it is restricted to only oneapplication per planting. Maintain green-house temperatures at 22 - 25ºC duringapplication. The mammalian acute toxic-

ity at the time of application is danger-

ously high, especially from breathing

vapours or smoke. (LD50

: oral = 50 - 60;dermal = 50). It is toxic to birds and beesbut has low residual toxicity.

pyrethrin plus Safer’s InsecticidalSoap (Trounce)

Trounce is a mixture of Safer’s insecticidalsoap and pyrethrin. Safer’s insecticidal soapis made of selected fatty acids that killinsects on contact. Thorough coverage of allleaf surfaces is essential as it kills only bycontact action at the time of application andhas no residual effect. It may injure soft planttissues. Do not spray plants in direct sunlightas burning may occur. Apply when weatherconditions promote slow drying such as earlymorning or late afternoon to evening. Mam-malian toxicity is low (LD

50: oral = 1,500

mg/kg: dermal > 1,800 mg/kg), but it maycause minor lung irritation from mist inhala-tion during application. Use an approved

respirator. Eye exposure to concentratedsoap may cause irritation. Pyrethrins aretoxic to bees and fish. For greenhouse pep-pers, applications may be made bi-monthlyor when aphids reach treatment levels. PHI is5 days.

pyridaben (DYNO-Mite, Sanmite)DYNO-Mite is a pyridazinone that acts as amitochondrial electron transport inhibitor; itblocks cell respiration causing the pest tolose motile co-ordination and eventually die.It is non-systemic with contact action, sothorough spray coverage is essential, espe-cially of the lower leaf surfaces. With spidermites, the most susceptible stages are thelarval and first two nymph stages(protonymphal and deutonymphal). The eggstage is less susceptible and the adult stage isleast susceptible. If adult females representmore than 15% of the population, then aproduct such as Avid that provides quickadult knock-down should be used beforeapplying DYNO-Mite. This product can beeffective against whiteflies in ornamentals.The full extent of its efficiency is not seenuntil 4 to 7 days after application; a pointthat should be considered when evaluatingits efficacy. It has a low mammalian acutetoxicity (LD

50: oral = 820 – 1350 mg/kg:

dermal > 2,000 mg/kg). For resistancemanagement purposes, it’s recommended notto use DYNO-Mite in successive applica-tions. Rotate sprays with at least one otherproduct before using it again. PHI is 3 days.

soap (Safer’s Insecticidal Soap)Insecticidal soap is an organic substanceconsisting of the salts of oleic acid - a natu-ral constituent of oils and fats. Thoroughcoverage of all surfaces of the sprayed plantsis essential as it kills only by contact actionat the time of application and has no residualeffect. It may injure soft plant tissues. Do notspray plants in direct sunlight as burning mayoccur. While its mammalian toxicity is verylow, it may cause minor lung irritation if


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inhaled during application. Use an approvedrespirator. Eye exposure to concentratedsoap may cause irritation. For greenhousepeppers, do not apply more than twice percrop cycle or within 3 days of harvest.

tebufenozide (Confirm)Confirm is an insect growth regulator used tocontrol Lepidopteran pests such as cabbageloopers. It is generally compatible with mostbeneficials but may impact those that gothrough moulting stages (e.g. Orius spp.).Timing and good coverage are an importantpart of control. Thorough, uniform spraycoverage is essential, and it should be usedon early larval stages. Larvae must eat theproduct on the leaves in order for it to work.Do not exceed 4 applications per year.

Confirm is in the moult accelerating com-pound (MAC) family; it mimics the action ofthe insect molting hormone, ecdysone, inlarval Lepidoptera (caterpillars). Larvae stop

feeding within hours after ingesting a toxicdose, although they may continue moving forseveral days. They begin to undergo anunsuccessful and lethal moult. Mortality timeis dependent upon the physiology of thetarget species and on environmental condi-tions. Generally death occurs between threeand ten days after ingestion. It is essentiallynontoxic to adult bees. It is toxic to certainaquatic invertebrates. Beneficials such aspredatory mites, beetles, wasps, and spidersare not adversely affected. It is irritating toskin upon repeated and prolonged contact. Ithas low mammalian toxicity (LD

50: oral >

5,000 mg/kg: dermal > 5,000 mg/kg).

For greenhouse peppers, apply to foliage notmore than 4 times per crop cycle or morefrequently than every 7 days. PHI is 3 days.Re-entry is 12 hours.


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Spraying Equipment

Sprayer Basics

High-Volume SprayersConventional pesticide application involveschemicals diluted in a large amount of water.The large amount of water (high-volume) is usedto produce comparatively large spray droplets(100 to 400 microns in diameter) and the spray isapplied until the foliage is visibly wet. High-volume, dilute sprays are well suited to low-pressure backpack sprayers; whereas low-volumebackpack sprayers do not achieve uniformcoverage. However, high-volume sprays tend towaste material as attempts to cover all thefoliage can result in excessive runoff.

Low-Volume SprayersLow-volume (LV) pesticide application refersto spraying pesticides at the label rate (per area)with much less water, requiring a more concen-trated spray mixture. A low-volume sprayerapplies the same quantity of active ingredientto a given area as does a high-volume sprayer.The term low-volume refers to the smallamount of water or diluent used to apply thepesticide. Low-volume spraying is sometimesreferred to as concentrate spraying. Low vol-ume in greenhouses is typically associated withmisters and foggers that are used only in green-houses. Misters and foggers are ultra-low-volume when compared to most conventionaloutdoor sprayers.

Droplet SizeSpray droplets are categorized by their sizewhich can vary greatly depending on the sprayequipment. Spray droplet size and typical usesare shown in Table 7-2.

Very small droplets are typically used in green-house misting or fogging operations and aregenerally termed low-volume, or even ultra-low-volume applications. The droplets are tiny enoughto remain suspended in the air for long periods.

Spraying with smaller droplets results in cover-ing the surface with less spray solution. Be-cause the volume of the droplet is based on thecube of the droplet diameter, 1,000 ten microndiameter droplets have the same volume ofwater as a single 100 micron diameter droplet.The 1,000 small droplets will cover the surfacearea much better than the single larger droplet.The smaller droplets are also much less proneto runoff than larger droplets and are moreeasily carried by the swirling air-stream to theundersides of leaves. While the science behinddroplet transport and impact on plant surfacesis complicated the results are not; smallerdroplets mean more area is covered with lesswater and less run-off.

Type of Spray Average Droplet Size (microns) Examples of Uses

Fog 0.1 - 5.0 compressed air and cold foggers

Coarse fog/fine mist 10 – 50 thermal foggers and rotary misters

Coarse mist 50 - 100 air-blast and high pressure sprays of insecticides or fungicides

Fine spray 100 - 250 conventional insecticide or fungicide sprays

Medium spray 250 – 500 herbicide sprays

Coarse spray 500 – 1000 herbicide ground sprays; root zone drenches

Table 7-2 Typical droplet sizes for various types of pesticide spray applications


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The disadvantage of smaller droplets is thatthey are more prone to drift in outdoor applica-tions due to wind conditions. Smaller dropletsare also more vulnerable to dry air conditionsthat may cause the water carrier to evaporatebefore the droplet lands on the target. In green-houses this may limit mister and fogger use tonight-time when workers are not present andwhen the venting systems can be closed tocontain the mist and fog within the greenhouse.Lack of venting would cause overheatingduring warm, sunny days. With these LVsprayers, the air circulation system is used tohelp distribute the pesticide spray throughoutthe greenhouse, so it is possible to apply pesti-cides without any workers in the greenhouse.By venting the greenhouses and observing there-entry times, potential worker exposure topesticides is reduced.

Monitoring Spray CoverageThe underlying issue of choosing high or lowvolume spraying and the type of pesticideapplication equipment should be which pro-vides the best coverage. If purchasing newequipment, arrange a demonstration where thetechnology can be evaluated for coverage.Obtaining complete coverage is critical to goodpest control and good coverage is not as obvi-ous when spraying with lower volumes that donot “wet the crop to the point of runoff ”.

Water sensitive paper available from mostsprayer supply companies can be attached totops and bottoms of leaves with paper clips.Spray drops of water will be visible as smallcoloured dots on the paper. Very fine dropletssuch as fogs and smaller mist droplets may betoo small to register on the water sensitivepaper. For these sprays buy a fluorescent dye tobe mixed in the water then view the leavesunder a black light to see the coverage of thespray droplets. Contact your supplier or localMinistry of Agriculture, Food and Fisheriesoffice for more information.

High-Volume SprayingEquipment

Backpack Sprayer for Spot TreatmentThe most common spraying equipment on smalloperations is the backpack sprayer. It is suitablefor high-volume or dilute spraying both in fieldand greenhouse conditions. Basic, low costbackpack sprayers generate only low pressuresand lack features such as diaphragm pumps,agitators, pressure adjustment controls (regula-tor), and pressure gauges found on commercialunits. These low-pressure sprayers withoutpressure regulators and gauges should not beused for applying insecticides and fungicideswhere uniform coverage is important.

Commercial quality sprayers with diaphragmpumps and agitators will allow more effectiveuse of wettable powder sprays. Pressuresshould be above 200 psi at the nozzle toachieve the finer sprays suitable for applyinginsecticides and fungicides. Pressure gauges andpressure regulators enable the sprayer to oper-ate at higher pressures (200+ psi) and theoperator to achieve a more uniform outputfrom the sprayer. Note that consistent walkingspeed and spray wand motion is also requiredto achieve uniform coverage. Nozzles must beselected for the operating pressure of thesprayer and spraying conditions. Backpacksprayers should have a positive shut-off spraycontrol valve to eliminate pesticide drips fromthe wand and nozzle. Drip-proof nozzle assem-blies are also available as an alternative. Ballcheck valves in the nozzle body require 5 to 10psi of liquid pressure to start spraying and closewhen the pressure drops below this level toprevent drips.


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Specialized GreenhousePesticide Equipment

Pesticide application equipment for green-houses is often differentiated by the kind ofparticle they produce, namely mists, fogs, orsmokes. A more accurate method to groupthem is by the method used to make the drop-lets rather than by the particle size. Technicallythe four pesticide applicators, mist blowers,thermal foggers, high-pressure applicators, andcompressed air systems, are all low volume mist(LVM) systems. They produce fine droplets,less than 100 microns in size and they use verylow water volumes. However, industry termi-nology generally only refers to the compressedair systems as LVMs. Table 7-3 compares thefour specialized greenhouse sprayer systems.

Mist BlowerA small engine and fan creates an air streamwith a velocity of 100 to 200 mph. Concen-trated spray injected into the air stream by aspecial nozzle is carried to the target by the air.Application is done by the applicator walkingthrough the greenhouse directing the nozzleinto the plant canopy to get good penetrationand coverage. Nozzles held too close to theplants might cause blast damage. For goodcoverage, the nozzle should be moved at a pacethat replaces the air within the canopy with airfrom the mist blower. They are suitable forlarge and small treatment areas. Greenhousesdo not have to be tightly sealed during applica-

tion; vents may remain open, but fans shouldbe turned off. Rotary misters use a spinningdisc to break up the spray into small droplets.The spray stream must be directed at the cropsand moved up and down to take advantage ofair turbulence and get good distribution. Somemanufacturers also include a fan behind thedisc to propel the spray towards the target andcreate a turbulent air stream. They are alsoreferred to as controlled droplet applicators androtary atomizers. Trade names include:“Ulvafan”, “Electrafan”, “Motafan”, and“Turbair”.

Thermal Fogging MachinesThermal foggers have been used for manyyears. They are usually gasoline-poweredbackpack or cart mounted units that are movedthroughout the greenhouse as they operate. Thepesticide is sprayed onto a hot element andevaporates. As it condenses it produces a heavyfog that drifts through the greenhouse andpenetrates the foliage. It covers both upper andlower surfaces of the leaves. Thermal foggersrequire specialized carrier solutions to producea visible fog, eliminate the evaporation ofdroplets, and ensure uniform particle sizes. Thepesticide is usually sold as a ready to use (RTU)formulation with the carrier included. Green-houses must be tightly sealed during applicationand for several hours afterwards to allow thefine particles to settle out of the air. Tradenames include: “Pulsfog”.

Sprayer Droplet

size (microns)

Tightly sealed

greenhouse

Moved by applicator or

stationary

Special carrier solution

Mist blower 60 - 80 no moved by applicator no

Thermal fogger 12 - 25 yes moved by applicator yes

High pressure 30 - 60 no moved by applicator no

Compressed air 5 or less yes stationary no

Table 7-3 Comparison of specialized greenhouse sprayers


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High Pressure Pesticide ApplicatorThis specialized greenhouse pesticide applica-tor uses very high pressure (1,000 to 3,000 psi)to create extremely fine sprays. Sprayers operat-ing at 3,000 psi can produce spray dropletsaveraging 30 to 60 microns in diameter that areprojected 20 to 25 feet from the spray gun. Asmall spray tank, motor, pump, long high-pressure hose, and handgun are all mounted ona small wheeled hand cart. The operator walksslowly through the greenhouse directing thespray ahead and into the crop. Special foggingformulations are not required. It is not neces-sary to tightly seal the greenhouse during appli-cation; vents may remain open, but fans shouldbe turned off. These sprayers are also referredto as mechanical foggers. Trade names include:“Coldfogger”.

Compressed Air or Aerosol GeneratorsThese devices use compressed air to break thespray liquid into small drops using an atomizingnozzle. The nozzles are usually placed in frontof a fan that disperses the spray into the green-house air.

These units are often used as stationarysprayers that rely on the greenhouse air move-ment system to circulate the aerosol throughoutthe foliage in the greenhouse. They are de-signed to operate unattended when staff arenot present. Good coverage depends uponproper placement in relation to the greenhouseair circulation system. It will not be effective ingreenhouses lacking adequate air movement.Special formulations are not required. Green-house must be tightly sealed for several hoursduring and after application. Trade namesinclude: “Autofog”.

Electrostatic SprayersThese are not a separate class of sprayers,rather it’s a feature that is found on some of thepreviously mentioned sprayers. Electrostaticsprayers electrically charge droplets as theyleave the nozzle. The charged droplets pen-etrate the foliage and adhere to all plant sur-faces, including the underside of leaves. An

advantage of this is that the electrically chargedparticles are attracted to the oppositely chargedleaf surfaces, providing good coverage of bothsurfaces. A disadvantage is that the foliage firstcontacted attracts so many spray particles thatthere are not enough left to contact foliagedeeper in the canopy.

Smoke Fumigators – CansA pesticide fog or smoke that comes in ready-to-use cans. When the fumigant is ignited, thesmoke carries the pesticide on air currentsthroughout the greenhouse. Each can is suffi-cient for a certain volume of greenhouse.Greenhouses must be tightly sealed during andafter application. They must only be usedwhen unprotected workers are not present.They have been used successfully in smallgreenhouse for many years. Trade namesinclude: Plant-fume Nicotine Sulphate.

Sprayer Components

Power SourceThe power-sprayer is normally driven by thepower-take-off (PTO) of a tractor or in green-houses, by an auxiliary engine. The powerrating of these should be double the theoreticalpower required by the pump.

PumpsA pump creates the pressure required for atomi-zation and penetration of the spray. For pres-sure requirements of pumps, choose a pumpthat has the specifications required for your job.The capacity of the pump should be deter-mined by the highest rate of application thesprayer is expected to deliver, plus an adequatevolume for agitation.

Common pumps include:

• roller pump, excessive wear can occur withwettable powders;

• piston pump;

• diaphragm pump.


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TanksThe size of the spray tank depends on theintended volumes of spray to be applied andthe ease of movement throughout the green-house. For ease of filling and accurate mixing,the tank should be marked off by volume,preferably in litres. The tank should beequipped with a large screened opening for fastfilling and easy cleaning. Tanks should beconstructed from stainless steel, fiberglass, orpolyethylene. Galvanized steel tanks are aheadache that should be avoided. Never use

Roundup or liquid nitrogen in galvanized

tanks. Either hydraulic by-pass or mechanicalagitation must be provided. If hydraulic agita-tion is used in the spray tank, additional pumpcapacity is required. Mechanical agitation ispreferred if wettable powders are to be usedbut can be a nuisance by causing excessivefoaming of materials that contain a high levelof wetting agent.

NozzlesThe size of droplet produced by various noz-zles depends upon operating pressure andnozzle opening. The droplet size decreaseswith increasing pressure and with decreasingdiameter of nozzle orifice.

Types

The main nozzle types used for chemical appli-cation are:

• Tapered flat-fan spray nozzles are used forlow volume, low pressure spraying such asthe application of herbicides to the soil.They are also known as fan type or T-jets.They produce a fan type pattern with lessmaterial applied along the edges of the spraypattern. By properly over-lapping the spray,a uniform application is produced across thearea covered by the spray boom.

• Even flat-fan spray nozzles produce an evenspray pattern across the entire fan width.These nozzles are used in band spraying ofherbicides where there is no overlap fromother nozzles, for example with a backpacksprayer having only one nozzle.

• Cone nozzles are used for high pressurespraying (mostly fungicides and insecticides).These nozzles produce a swirling mist so thespray material can reach the undersides ofleaves. They are available as either hollowcone or solid cone types - both produce thesame swirling mist but the solid cone nozzlesare used when larger volumes are required.The most commonly used cone nozzles arethe two-piece disc-core nozzles. They mustbe correctly installed with the rear nibs facingthe base of the nozzle body (see Figure 7-2).Various sizes of swirl plates and orifices canbe fitted in the same nozzle body.

Sizes

Various sizes of flat and cone nozzles may beused to obtain the volume of application desired.Your sprayer equipment supplier has tablesshowing flow rates for different nozzle sizes.

Materials

Nozzles are made from a variety of materials.Choice of material depends upon theabrasiveness of the spray mixture. Wettablepowders are more abrasive than emulsions.Brass tips are cheap but the metal is soft and thetips wear faster than the more expensive tips. Insequence of durability from least to most, thefollowing materials are used: brass, stainlesssteel, hardened stainless steel, ceramic, andtungsten carbide. For greenhouse applications,where not many nozzles are required, only thebest materials should be used.

As nozzles wear out, the volume of applicationincreases. For this reason, frequent calibrationof equipment is necessary.

Figure 7-2. Assembly of disc-core cone nozzle


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ScreensScreens prevent larger particles from enteringthe system, clogging nozzles and wearing outthe pump.

There should be screens in the tank opening,between the tank and the pump, and in thenozzle tips. Suction strainers, line strainers andnozzles should all be equipped with 50 meshscreens when wettable powders are to be used.Screens finer than 50 mesh, for example 100mesh, may prevent the unrestricted flow ofsome wettable powders. Screens are generallyused in fine nozzles, but slotted strainers can beused in those that have a larger opening, andwith cone nozzles. Clean screens and strainersare essential to the efficient operation of thespray system. They should be cleaned oftenand checked for breaks in the mesh.

Mixing Chemicals

When mixing the chemical in the sprayer tank,NEVER put the chemical in first and then topup with water. Always fill the tank 1/3 to 1/2full with clean water, spray out a small amountof water to ensure the system is working prop-erly and then add the required quantity ofchemical with the agitator running. Continuethe agitation while continuing to fill the tank.If two or more chemicals are to be appliedtogether, first check the labels for compatibilityand then add the first chemical at the 1/3 to 1/2 full stage and the second chemical at the 2/3to 3/4 full stage. Mixing by this method willensure that both chemicals are completelymixed in the water. Wettable powders can bepremixed before being added to the spray tank.Make a slurry of wettable powder and waterand then pour it into the spray tank. Alwaysfollow manufacturers’ directions when mixing.Always keep the agitator running once thespray materials have been added to the tank.However, for liquid pesticides with highlyactive wetting agents, it is better to add thepesticide just before filling is complete to avoidexcessive foaming.

Sprayer Cleaning

Immediately after use, flush the sprayer withsoapy water and then rinse with clean water.Select a cleaning area where wash water will notcontaminate wells, streams, drainage ditches orareas frequented by workers or animals.

Even stainless steel nozzles will rust if left inthe sprayer. Nozzles and nozzle screens shouldbe removed, cleaned and stored in a can of lightoil or diesel fuel if the sprayer is not going to beused for several weeks. After a spray applica-tion, the nozzles should be cleaned and coatedwith a light coat of oil to prevent corrosion.Ceramic nozzles are not subject to corrosion.

Sprayer CalibrationCalibration helps ensure good pest control. Italso helps prevent potential crop damage, highpesticide residues, and environmental contami-nation. All application equipment should becalibrated to ensure that pesticides are appliedaccurately and uniformly at the recommendedrate. Calibration involves preparing the equip-ment so it is working properly, measuring thedelivery rate, adjusting the equipment tochange the delivery rate, and calculating howmuch pesticide to add to the sprayer tank.Calibrate equipment regularly, at least once peryear, to make sure the output is not changing.Also calibrate equipment when it is new andwhen making changes that affect the deliveryrate. Proper calibration will minimize, if noteliminate, leftover pesticide solutions in thesprayer tank that can be very difficult to dis-pose of properly.

There are four basic procedures to be carriedout when calibrating almost any sprayer. Detailson these procedures are given below.

1. Set-up.

2. Measuring delivery rate.

3. Adjusting delivery rate (if different fromrecommended rate).

4. Calculating how much pesticide to add to thespray tank.


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Calibration of back pack sprayers, boomsprayers and specialized greenhouse sprayers willbe discussed. All spraying equipment should becalibrated using the same basic steps; morecomplex equipment may require more setup.

Set-Up

Set-up is often the most neglected componentof calibration and without proper set-up thelikelihood of good spray coverage and uniform-ity is greatly diminished. The reason why set-upis often neglected is that it takes time, lots oftime, if the sprayer has not been well-main-tained. During sprayer set-up, check that thesprayer nozzles and spray pressure suit thepesticide, crop conditions and pest conditions.Check the equipment to ensure all parts are ingood working order. Refer to the sprayer’soperating manual for specific operating instruc-tions. All sprayers should be properly set-upbefore you move on to the second step incalibration, measuring the delivery rate.

Selecting Spray Volume

Many pesticides used for greenhouse crops aregiven as dilution rates where the crop is to besprayed thoroughly. Spraying a test area of thecrop, say 100m2, with water will allow theoperator to calculate the amount of waterrequired to adequately cover a hectare bysimply multiplying the volume of spray used X100 because one ha is 100 times larger than100m2. This technique is useful to determinethe amount of pesticide needed per hectarewhen labels only provide the recommended ratein volume of water.

The same technique can be used to identify thevolume of water required to cover one ha andthus the quantity of pesticide that must beadded to that volume of water when the labelrate is expressed as a certain amount of pesti-cide per ha. Keep in mind that the spray vol-ume changes with size of plants, pest condi-tions, and method of application.

For high volume application of fungicides andinsecticides, volumes of 300 to 1000 L/ha are

typically used, unless otherwise specified. Forfoliar sprays, just enough water should be usedto obtain thorough coverage of the leaveswithout run-off. Early in the season whengrowth is light, 300 L/ha of water may beadequate. In situations where foliage is denseand coverage is critical, at least 1,000 L/ha ofwater should be used. For drenches (high-volume, low-pressure sprays directed to the soilfor control of soil-borne pests), usually at least2,000 L/ha is used

To maintain effective coverage of the foliagewith lower spray volumes, finer droplets arerequired to cover the same area. Finer dropletsare more prone to drift and harder to spray intodense foliage. In hot, dry conditions, low ambi-ent relative humidity may cause the water infine droplets to evaporate before the pesticidereaches the target. This is another cause ofdrift. Sprayer operators should carefully moni-tor the foliage including the lower stems andundersides of lower leaves to ensure thoroughcoverage. Water-sensitive spray cards areavailable to assist in carrying out this task.

Selecting Nozzle Pressure

Insecticides and fungicides are applied atpressures up to 2,000 kPa (300 psi) in conven-tional spraying equipment depending upon thepest to be controlled, the type of pesticide, andthe density of the foliage. For non-systemicpesticides and high, dense plant canopies, highnozzle pressures should be used to penetrateand cover the foliage. Systemic pesticides andplants with open canopies can be sprayed atlower nozzle pressures, generally 550 kPa (80psi) and higher. Commercial quality backpacksprayers will produce pressures up to 1,000 kPa(150 psi). These units should be equipped witha pressure gauge and pressure regulator just likea powered sprayer. Some manufacturers supplykits to convert backpack sprayers that do nothave these components.

Many nozzle manufacturers have chosen toreport nozzle outputs with pressures in “bars”not kilopascals (kPa). The bar unit is equal to


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100 kPa. Pesticide labels report pressures inkPa. Use a pressure gauge on the sprayermarked in both psi and kPa (or bar) so bothunits can be read directly from the gauge. Themaximum pressure on the pressure gauge forpowered sprayers should be twice the maximumpressure of the pump to protect the gauge fromdamage and allow it to be read accurately.

Calibrating Boom Sprayers

Preparing Your EquipmentBefore calibrating, make sure all nozzles,screens, and filters are clean; the pressure gaugeis giving an accurate reading; all hoses are ingood condition; there are no leaks in the sys-tem; and the agitation system is working.

Select the right nozzle tips for the type of sprayingyou are planning. Changing tips affects sprayeroutput. Disc type hollow cone nozzles are suitablefor most insecticides and fungicides applied withvertical spray booms. Check each nozzle to makesure that the output is the same for all.

To check output:

1. Select desired pressure, e.g. 500 – 1500 kPa.

2. With the sprayer operating at the desiredpressure, collect output from each nozzle for30 seconds.

3. Using a suitable-sized graduated cylinder,record the output from each nozzle andcalculate the average. (Average output = totaloutput of all nozzles / number of nozzles)

4. Replace any nozzles which are more than 5%above or below the average, or which have avisibly distorted spray pattern.

5. As nozzles wear, output increases. If outputhas increased 15% above the output whenthe nozzles were new, replace them.

Calibration MethodFind the delivery rate (output) by measuring theamount of spray applied to a test area by:

1. Accurately measure and mark a reasonablylong test strip in the greenhouse, e.g. 100 m.

The longer the test strip, the more accuratethe calibration.

2. Place a carefully measured volume of waterin the spray tank.

3. Set the pressure at the desired position.

4. Spray the test strip. Open the boom valve asyou pass the first marker and close it as youpass the second. Make sure you are usingthe selected pressure and are moving at thedesired speed when you spray the test strip.

5 Drain the sprayer into a measuring containerand determine the volume of water that hasbeen used.

6. Calculate the sprayer output by using thefollowing formula: Delivery rate in L/ha =(litres used X 10,000) divided by (boomwidth in metres X length of test strip inmetres)

Adjusting Sprayer Delivery RateIf the measured delivery rate of your sprayer isdifferent than the spray volume recommendedon the pesticide label or in the productionguide, it can be adjusted in three ways:

1. Nozzle size can be changed. Check the tableof nozzle sizes that came with your sprayeror get the information from your supplier. Alarger orifice gives higher output and smallergives lower output.

2. Adjusting the speed of moving up the rowwill change the output. Moving twice as fastwill cut the output by 50%.

3. Spray pressure should be set for the correctdroplet size. Changing pressure is recom-mended only for very small changes in deliv-ery rates. Otherwise the droplet size willchange and cause drift or runoff problems.Since pressure must be increased four timesto double the delivery rate, this is not a goodway to adjust delivery rate.

After making the adjustments, measure thedelivery rate again!


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Calibrating Hand OperatedSprayers

Sprayer Set-UpHand operated sprayers should be checked tomake sure that there are no leaks, especiallywhere the hose enters the tank and around thetrigger valve. The nozzle should deliver auniform spray pattern. Many nozzles can beadjusted to produce the desired droplet size.Adjust the nozzle to produce a coarse spraywith larger droplets, for herbicides and mediumto fine spray with smaller droplets, for insecti-cide and fungicide applications.

For uniform spray application it is important tomaintain a constant spray pressure. Somemanufacturers offer pressure regulators andpressure gauges as optional accessories thatenable the operator to set specific pressuresdepending on the spraying job. Commercialquality backpack sprayers should have these asstandard equipment. Uniform spray applicationalso requires the operator to co-ordinate thewalking speed with uniform sweeping move-ments of the nozzle. The back and forth move-ments determine the swath width.

Most pesticide labels give instructions as aspecific amount of pesticide per unit area (e.g.,apply 2.4 L/ha). Some labels give instructionsas a specific amount of pesticide in a givenvolume of water sufficient to give thoroughand complete coverage (e.g. apply 2.4L/500Lof water). Some labels give both (e.g. apply2.4L/500L of water/ha).

Application Rate Given as a Dilutionwith WaterPesticide labels sometime give instructions todilute an amount of pesticide in water andapply to runoff.

Example: A label recommends mixing 175grams of a pesticide product in 100 litres ofwater and applying until it runs off of thefoliage. If you have a 12 litre backpack you mustcalculate how much pesticide to add to the tankusing the following formula: Amount of pesti-

cide in grams to add to spray tank = (175 gramsdivided by 100 L) X 12L = 21 grams.

Before filling the sprayer, spray a test strip withone litre of water to determine how many litresyou will need to spray the whole area. If onelitre covers 30 metres and you want to spray500 metres, you will need (500 divided by 30)X (1 litre divided by 12 litres) = approximately1.4 tankfulls to spray the area.

Application Rate Given as Amountof Pesticide per HectarePesticide labels sometimes give instructions toapply a specific amount of pesticide per unitarea (e.g. apply 2.5 litres per hectare). Tocalibrate your sprayer for this type of ratefollow these steps:

First measure the delivery rate or the output ofyour sprayer by:

1. Accurately measuring and marking a teststrip, e.g. a 20 metre strip.

2. Measure the width of the spray swath. Thespray width varies with the type of nozzleused and the distance between the targetand the nozzle.

3. Measure several litres of water into thespray tank. Pump the hand lever to theoperating pressure you will be using.

4. Spray over the measured test strip whilemaintaining a steady, uniform walking speedand a steady pumping pace. Variation inspeed and pumping pressure will change theoutput.

5. Drain the spray tank, measuring the volumeof water left. Calculate the volume of waterused.

6. Calculate the sprayer delivery rate (output)by using the following formula: Sprayerdelivery rate (L/ha) = (litres used X10,000m2) divided by (spray width in metersX test length in metres).


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Example: The test strip is 20 m long, the spray swath is 1 m wide. The amount of watersprayed during the test is 2.5 litres. Sprayer output is:

2.5 L x 10,000 = 25,000 = 1250 L/ha1 m x 20 m 20

Secondly, calculate the area that can be treated with a full tank.

Area sprayed by 1 tank = Volume of spray mixture in tankDelivery Rate

For example, if your backpack sprayer has a capacity of 12 litres and you calibrated the sprayerdelivery rate based on your walking speed at 1250 L/ha then one full tank will cover

12 L = 0.0096 ha 1250 L/ha

Thirdly, calculate the amount of pesticide to add to the spray tank as follows:

Amount of pesticide = Application x Area sprayed by to add to tank rate one tank

Example: A label says to use 4 L/ha of pesticide product and you calculated that one 12 Lbackpack will cover .0096 hectares.

Amount of pesticide = 4 L/ha x .0096 ha = 0.0384 L or 38.4 mL to add to tank

Approximate Quantities to Use In Backpack Sprayers Using MetricMeasurementFungicides, Herbicides, Insecticides (using a volume of 1000L/ha)

Liquids — If recommendation is 1 L/ha use 100 mL in approximately 100 L of water per1000 m2 or 1 mL in approximately 1 L of water per 10 m2.

Wettable or Soluble Powders — If recommendation is 1 kg/ha, use 100 g in 100 L of waterper 1000 m2 or 1 g in 1 L of water per 10 m2.


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Preparation of Nutrient SolutionsThe following tables are adapted from: Sonneveld, C. A Method for Calculating the Composition ofNutrient Solution for Soilless Culture. Some growers may find useful information in them.

Definitions:

– molar solution = molecular weight of fertilizer ingredient in grams per litre of water;

– millimolar (mmol) solution = molecular weight in milligrams per liter of water;

– micromolar (µmol) solution = molecular weight in micrograms per litre of water;

– milligrams per litre (mg/L) = parts per million (ppm);

– molecular weight of fertilizer ingredient = sum of the atomic weights of the elements making upthe ingredient (see Table 8-1).

Conversion of millimoles per litre to parts per million:

– consult Table 8-1 to obtain molecular weight;

– multiply molecular weight X mmol required = ppm

– for example, a 3 mmol solution of ammonium nitrate would be 3 X 80 = 240 ppm

Conversion of parts per million in the feed solution to kilograms per cubic metre (1000 litres) in the100X concentrated stock solution:

– kilograms of fertilizer / 1000L = ppm of the final feed solution / 10

– for example, 240 ppm feed solution of ammonium nitrate would require 240/10 = 24 kg.

Tables 8-2, 8-3, 8-4, and 8-5 give the fertilizer quantities in grams or kilograms required to make up100X concentrated stock solutions for various levels of feed solutions.


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Table 8-1. Molecular weights for various fertilizers Fertilizer Chemical Nutrient Molecular Compound Formula Content (%) Weight

Nitric acid (100%)* HNO3 22 N 63

Phosphoric acid (100%)* H3PO4 32 P 98

Sulphuric acid (100%)* H2SO4 33 S 98

Calcium nitrate Ca(NO3)2 15.5 N, 19 Ca 200**

Potassium nitrate KNO3 13 N, 38 Kt 101.1

Ammonium nitrate NH4NO3 35 N 80

Magnesium nitrate Mg(NO3)2.6H2O 11 N, 9 Mg 256.3

Mono potassium phosphate KH2PO4 23 Pt, 28 Kt 136.1

Mono ammonium phosphate NH4H2PO4 12 N, 27 Pt 115

Potassium phosphate K2SO4 45 Kt, 18 S 174.3

Magnesium sulphate MgSO4.7H2O 9.8 Mg, 13 S 246.3

Manganese sulphate MnSO4.H2O 32 Mn 169

Zinc sulphate ZnSo4.7H2O 23 Zn 287.5

Borax Na2B4O7.10H2O 11 B 381.2

Solubor Na2B4O7 21 B 201.2

Copper sulphate CuSO4.5H2O 25 Cu 249.7

Sodium molybdate Na2MoO4.2H2O 40 Mo 241.9

Iron chelate liquid Fe – DTPA 3.8 Fe 1471tt

iron chelate liquid Fe – DTPA 6.1 Fe 916tt

iron chelate Fe – EDTA 13 Fe 430tt

iron chelate Fe – EDDHA 6 Fe 932tt

potassium bicarbonate KHCO3 39 K 100.1

calcium hydroxide Ca(OH)2 54 Ca 74.1

sodium bicarbonate NaHCO3 19 Na 75

* Calculations must take into account that acids are available in concentrations of less than 100%. i.e. nitric acid @ 67%, phosphoric acid @ 75%, and sulphuric acid @ 93%. ** Calcium nitrate also contains crystallization water and some ammonium nitrate so molecular weight is only an estimate. t The % P & K do not agree with the labelled fertilizer analysis because P is expressed as P2O5 and K as K2O in fertilizers. To convert P to P2O5, multiply by 2.29; K to K2O, multiply by 1.205. tt Iron chelate molecular weights are only estimates calculated on the basis of iron content.


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Table 8-2. Quantities of acids and salts to add to 1000 litres to make 100X stock solution.

Concentration Nitric Phosphoric Potassium Ammonium Monopotassium of Feed Acid Acid Nitrate Nitrate Phosphate Solution HNO3 H3PO4 KNO3 NH4NO3 KH2PO4

(mmol/L) (kg)* (kg)* (kg) (kg) (kg) 0.5 3.2 4.9 5.1 4.0 6.8 1.0 6.3 9.8 10.1 8.0 13.6 1.5 9.4 14.7 15.2 12.0 20.4 2.0 12.6 19.6 20.2 16.0 27.2 2.5 15.8 24.5 25.3 20.0 34.0 3.0 18.9 29.4 30.3 24.0 40.8 3.5 22.0 34.3 35.4 28.0 47.6 4.0 25.2 39.2 40.4 32.0 54.4 4.5 28.4 44.1 45.5 36.0 61.2 5.0 31.5 49.0 50.6 40.0 68.0 5.5 34.6 53.9 55.6 44.0 74.9 6.0 37.8 58.8 60.7 48.0 81.7 6.5 41.0 63.7 65.7 52.0 88.5 7.0 44.1 68.6 70.8 56.0 95.3 7.5 47.2 73.5 75.8 60.0 102.1 8.0 50.4 78.4 80.9 64.0 108.9 8.5 53.6 83.3 85.9 68.0 115.7 9.0 56.7 88.2 91.0 72.0 122.5 9.5 59.8 93.1 96.0 76.0 129.3 10.0 63.0 98.0 101.1 80.0 136.1 * Quantities listed are for 100% acid; increase amount to take into account the actual concentration being used. e.g. for 1 mmol nitric acid, add 6.3 kg x 100/67 = 9.4 kg of 67% acid.

Table 8-3. Quantities of salts to add to 1000 litres to make 100X stock solution.

Concentration Potassium Calcium Potassium Magnesium of Feed Bicarbonate Nitrate Sulphate Sulphate Solution KHCO3 Ca(NO3)2 K2SO4 MgSO4.7H2O (15.5%N) (mmol/L) (kg) (kg) (kg) (kg) 0.25 8.3 5 4.4 6.2 0.5 16.6 10 8.7 12.3 0.75 24.9 15 13.1 18.5 1.0 33.3 20 17.4 24.6 1.25 41.6 25 21.8 30.8 1.5 50.0 30 26.1 37.0 1.75 58.3 35 30.5 43.1 2.0 66.6 40 34.9 49.3 2.25 74.9 45 39.2 55.4 2.5 83.2 50 43.6 61.6 2.75 91.5 55 47.9 67.8 3.0 99.9 60 52.3 73.9 3.25 108.2 65 56.6 80.1 3.5 116.6 70 61.0 86.2 3.75 124.9 75 65.4 92.4 4.0 133.2 80 69.7 98.6 4.25 141.5 85 74.1 104.7 4.5 149.8 90 78.4 110.9 4.75 158.1 95 82.8 117.0 5.0 166.4 100 87.2 123.2


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Table 8-4. Approximate quantities of iron chelates to add to 1000 litres to make 100X stock solution.

Concentration of Feed Solution

( mol/litre)

13% iron chelate (EDTA) grams

6% iron chelate (EDDHA)

grams

6.1% iron chelate (DTPA)

millilitres

3.8% iron chelate (DTPA)

milliltres

5 215 466 458 736

10 430 932 916 1471

15 645 1398 1374 2207

20 860 1864 1832 2943

25 1075 2330 2290 3679

30 1290 2796 2748 4415

35 1505 3262 3206 5151

40 1720 3728 3664 5887

45 1935 4194 4122 6623

50 2150 4660 4580 7359

55 2365 5126 5038 8095

60 2580 5592 5496 8831

65 2795 6058 5954 9567

70 3010 6524 6412 10303

75 3225 6990 6870 11039

80 3440 7456 7328 11775

85 3655 7922 7786 12511

90 3870 8388 8244 13247

95 4085 8854 8702 13983

100 4300 9320 9164 14719

EDTA chelating agent is used in pH range of 5 – 7.5; DTPA is effective over a wider range; EDDHA is effective over a still wider range, as high as pH 9.


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Table 8-5. Quantities of minor elements to add to 1000 litres to make 100X stock solution.

Conc. of

Feed Sol’n. mol/L

MnSO4

.H2O

grams

Conc. of

Feed Sol’n. mol/L

ZnSO4

.7H2O

grams

Na2B4O7*.10 H2O

grams

Conc. of

Feed Sol’n mol/L

CuSO4

.5 H2O

grams

Na2MoO4

.2 H2O

grams

2 34 1 29 38 0.1 2.5 2.4

4 68 2 58 76 0.2 5.0 4.8

6 101 3 86 114 0.3 7.5 7.3

8 135 4 115 152 0.4 10.0 9.7

10 169 5 144 191 0.5 12.5 12.1

12 203 6 172 229 0.6 15.0 14.5

14 237 7 201 267 0.7 17.5 16.9

16 270 8 230 305 0.8 20.0 19.4

18 304 9 259 343 0.9 22.5 21.8

20 338 10 288 381 1.0 25.0 24.2

22 372 11 316 419 1.1 27.5 26.6

24 406 12 345 457 1.2 30.0 29.0

26 439 13 374 496 1.3 32.5 31.4

28 473 14 402 534 1.4 35.0 33.9

30 507 15 431 572 1.5 37.5 36.3

* 1 mol Na2B4O7.10 H2O) = 4 mol B.


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Calculating Parts Per Million

Parts Per Million1 per cent = 10,000 parts per million

Imperial:1 fl. oz./gallon = 6250 ppm1 gallon in1,000,000 gallons of water = 1ppm1 litre in 1,000,000 litres of water = 1ppm = 1 mL/1,000 L

Metric:1 mg/litre (water) = 1 ppm1 g/litre (water) = 1000 ppm1 mL/litre = 1000 ppm

Metric Units for Farm Sprayers

Tank Capacities PressuresImp. gal litres (L) US gal. litres (L) pounds per square inch (psi) kilopascals (kPa)

100 455 100 379 10 70200 910 200 758 15 100250 1138 250 948 20 140300 1365 300 1137 25 175400 1820 400 1516 30 200500 2275 500 1895 35 240600 2730 600 2274 40 275800 3640 800 3032 45 310

1000 4550 1000 3790 50 345

LINEAR MEASURES10 millimetres (mm) = 1 centimetre100 centimetres = 1 metre (m)1000 metres = 1 kilometre

SQUARE MEASURES (AREA)100 m X 100 m = 10,000 m2

= hectare (ha)100 ha = 1 square kilometre (km2)

CUBIC MEASURES (VOLUME)Dry Measure1000 cubic millitres (mm3) = 1 cubic metre (m3)1,000,000 cm3 = 1 cubic metre (m3)Liquid Measure1000 millilitres (mL) = 1 litre (L)100 L = 1 hectolitre (hL)

WEIGHT-VOLUME EQUIVALENTS (FOR WATER)(1.00 kg) 1000 grams = 1 litre (1.00 L)(0.50 kg) 500 g = 500 mL (0.50 L)(0.10 kg) 100 g = 100 mL (0.10 L)(0.01 kg) 10 g = 10 mL (0.01 L)(0.001 kg) 1 g = 1 mL (0.001 L)

WEIGHT MEASURES1000 milligrams (mg) = 1 gram (g)1000 g = 1 kilogram (kg)1000 kg = 1 tonne (t)1 mg/kg = 1 part per million (ppm)

DRY – LIQUID EQUIVALENTS1 cm3 = mL1 m3 = 1000 L

The Metric System

Table 8-6. Useful Measurements


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ConversionImperial Units Factor Metric Units

oz./acre 70 g/halb./acre 1.12 kg/habu./acre 0.9 hL/hatons/acre 2.24 t/hafl. oz./acre 70 mL/hapt./acre 1.4 L/haqt./acre 2.8 L/hagal./acre 11.2 L/hagal./acre (US) 9.35 L/haplants/acre 2.47 plants/haoz./gal. 6.2 mL/Llb./gal. 0.1 kg/Loz./sq.ft. 305 g/m2

lb./sq.ft 4.9 kg/m2

oz./ft.row 93 g/m rowlb./ft.row 1.5 kg/m rowft./sec. 0.3 m/sm.p.h. 1.6 km/hp.s.i. 6.9 kPa

To convert from imperial to metric, multiply by theconversion factor.For example: 10 inches x 2.5 = 25 centimetres

To convert from metric to imperial, divide by theconversion factor.For example: 25 centimetres ÷ 2.5 = 10 inches

Imperial Conversions:

lb/acre x 0.0033 = oz/yd2

gal/acre x 0.033 = oz/yd2

ConversionImperial Units Factor Metric Units

LENGTHinches 2.5 centimetres (cm)feet 30 centimetres (cm)feet 0.3 metres (m)yards 0.9 metres (m)miles 1.6 kilometres (km)

AREAsquare inches 6.5 square centimetres (cm2)square feet 0.09 square metres (m2)acres 0.40 hectares (ha)

VOLUMEcubic inches 16 cubic centimetres (cm3)cubic feet 0.03 cubic metres (m3)cubic yards 0.8 cubic metres (m3)fluid ounces 28 millilitres (mL)pints 0.57 litres (L)quarts 1.1 litres (L)gallons (Imperial) 4.5 litres (L)gallons (US) 3.75 litres (L)bushels 0.36 hectolitres (hL)

WEIGHTounces 28 grams (g)pounds 0.45 kilograms (kg)short tons 0.9 tonnes (t)

TEMPERATUREdegrees degreesFahrenheit (F - 32) 0.56 Celsius (oC)

POWERhorsepower 750 watts (w)

0.75 kilowatts (kw)

Useful Measurements

1 Imperial gallon = 4 quarts= 8 pints= 160 fluid ounces= 10 pounds of water= approx. 1.2 US gallons

1 U.S. gallon = 0.8345 or approx. 5/6 Imperial gallon= 8.3 pounds

1 Imperial pint = 20 fluid ounces = 570 mL1 U.S. pint = 16 fluid ounces = 475 mL1 pound = 16 ounces1 tablespoon = 3 teaspoons = 14 mL2 tablespoons = 1 fluid ounce = 28 mL1 pound in

100,000 gallonsof water = 1 ppm (part per million)

1 mile = 5,280 feet= 1,760 yards

1 yard = 3 feet= 36 inches

1 foot = 12 inches1 acre = approx. 209 by 209 feet

or 43,560 square feet.1 square yard = 9 square feet1 square foot = 144 square inches1 mile an hour = 88 feet a minute1 cubic yd = 27 cubic feet

Litres per hectare x 0.4 = litres per acreKilograms per hectare x 0.4 = kilograms per acre

Useful Measurement – English System


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Glossary

active ingredient : the portion of a pesticideproduct that is toxic to the target organism.

acute toxicity: ability of a substance to causeill effects shortly after exposure; e.g. LD

50

values of pesticides refer to acute toxicity.

ADT: average daily temperature over 24 hr; forgreenhouse pepper production, ADT rangesfrom 15° to 25°C. For how to calculate, seeTable 3-2, page 16.

adjuvant: a chemical additive that improvesthe performance of a pesticide mixture.

adventitious: roots or shoots arising on occa-sion from unusual places on the plant.

a.i.: active ingredient.

anion: a negatively-charged ion, e.g. NO3

-, Cl-

antenna (pl. antennae): the paired segmentedsensory organs, borne one on each side ofthe head of insects; commonly termed hornsor feelers.

anthers: the pollen-producing organs of flowers.

bar: a unit of pressure = 100kPa (approxi-mately 15psi)

BER: blossom-end rot; a physiological disorderof peppers and tomatoes related to waterand calcium shortage in the fruit.

biological control (biocontrol): the action ofparasites, predators, or pathogens in main-taining another organism’s population densityat a lower average level than would occur intheir absence. Biological control occursnaturally in the field but may be enhanced bymanipulation or introduction of biologicalcontrol agents by people.

calyx: the sepals of a flower; they surround the

petals and enclose the unopened flower bud.

canopy: leafy parts of vines or trees; theoverhanging foliage of greenhouse vegetablecrops.

caterpillar: larva of a butterfly, moth, sawfly,or scorpionfly.

cat-facing (monkey-facing): disfigurement ormalformation of fruit; in the case of straw-berries, usually the result of injury to devel-oping achenes by lygus bugs, frost injury orboron deficiency.

cation: a positively-charged ion, e.g. H+, Ca++.

chelate: a complex molecule combining ametallic ion with an organic(carbon-contain-ing) portion; frequently used as a means ofsafely supplying a minor element to a plant.

chlorosis: yellow colour of a plant that shouldbe green; may be due to nutrient imbalance,chemical toxicity, or virus infection.

chronic toxicity: ability of a substance tocause ill effects over the long term ratherthan in the short term, e.g. cancer .

compatibility: ability of two chemicals to becombined without any adverse effects; abilityof biocontrol agents to function in thepresence of chemicals and/or otherbiocontrol agents.

contact pesticide: a pesticide that must con-tact the outside of an insect or weed in orderto control it; not systemic.

cornicles: two tubular structures located onthe posterior part of an aphid’s abdomen.

D: abbreviation for dust formulation of apesticide.

dead zone: the difference between the heat setpoint and the vent opening set point in agreenhouse.


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dew point: The temperature at which watervapour in the air will condense to form waterwhen in contact with a cooler surface such asplant leaves.

DF: abbreviation for dry flowable formulationof a pesticide.

diapause: a period of physiologically control-led dormancy in insects.

drench: high volume pesticide application(>2000L/ha); usually to the soil at the baseof a plant.

EC: electrical conductivity of a solution ex-pressed as mS/cm, an indicator of nutrientconcentration; in pesticide terms, anemulsifiable concentrate formulation.

ectoparasite: parasite that lives on the outsideof its host, e.g. a nematode that feeds fromthe outside of a root, using a long stylet.

emulsifiable concentrate (EC): a pesticideformulation containing a toxicant in asolvent and an emulsifier that allows it tomix with water.

endoparasite: a parasite that lives inside itshost, e.g. Encarsia in a whitefly scale.

entomophagous nematodes: nematodes thateat insects.

F: abbreviation for flowable pesticide formula-tion in which finally ground particles aresuspended in liquid that mixes readily withwater; an improvement on WP formulations.

fumigation: the use of chemicals in gaseousform to kill pests in confined structures,such as greenhouses or in the air pocketswithin the soil.

G: granular formulation of a pesticide, usuallyspread on the soil to control weeds or soil-inhabiting insects; usually not safe to useinside greenhouses.

honeydew: An excretion from insects, such asaphids, mealybugs, whiteflies, and softscales, consisting of modified plant sap;usually colonized by sooty mould fungi thatinterfere with photosynthesis in the leaves.

host: a plant or animal that provides suste-nance for another organism.

hyper-parasite: a parasite living inside anotherparasite that may be living inside a host;interferes with the effectiveness of abiocontrol program.

inoculum: bacterial or fungal cells that cancause disease if they contact a susceptiblehost.

instar: the larval or nymph stage of an imma-ture insect between successive moults.

IPM : integrated pest management ; using allavailable means to safely and sustainablycontrol pest and disease problems withminimal impact on the environment.

IRGA : infrared gas analyzer ; used for moni-toring and controlling CO

2 level in the green-

house.

L or LC: liquid formulation of pesticide ;properties are similar to EC formulations.

LAI : leaf area index; the ratio of plant leafarea to ground area beneath the plant ; formaximum light interception, the LAI forpeppers should be at least 3.

LD50

: lethal dose of a pesticide that kills halfthe animals, (usually rats or mice), in afeeding trial ; gives an indication of acutetoxicity to humans but tells nothing aboutchronic toxicity; the lower the LD

50, the more

toxic the chemical.

larva (pl. larvae) : immature insects thatdevelop during the process of completemetamorphosis from egg, through severallarval stages, pupa, and adult. In mites, thefirst-stage immature is also called a larva.


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microbial pesticide: pesticide that consists ofbacteria, fungi, viruses, or other microorgan-isms used for control of weeds, inverte-brates, or plant pathogens.

monitoring: carefully watching and recordinginformation on the activities, growth, devel-opment, and abundance of organisms orother factors on a regular basis over a periodof time, often utilizing very specific proce-dures; monitoring pest populations in a cropis one of the basic components of an IPMprogram.

molecular weight: the weight of a moleculeexpressed as the sum of the atomic weightsof its constituent atoms.

moult: insects and other arthropods shed skinbefore entering another stage of growth

MRL: maximum residue limit of a pesticidethat may be on a food product when itreaches the market; usually expressed asparts-per-million or parts-per-billion

mummy: the crusty skin of an aphid or otherinsect whose inside has been consumed by aparasite.

mycelium: the vegetative part of a funguscomposed of a network of fine threadscalled ‘hyphae’.

natural enemies: predators, parasites, andpathogens that feed on other insects, mites,pathogens, etc.; may be exploited by man toprovide biological control of pests.

necrosis: death of plant cells indicated bydarkening and desiccation; often the nextstage after severe chlorosis.

nectary: flower or plant gland that secretesnectar; honeybees collect nectar to makehoney.

nematicide: a pesticide used to control nema-todes.

nymph: the immature stage of insects such asgrasshoppers and aphids, that hatch fromeggs and gradually acquire adult formthrough a series of moults without passingthrough larval or pupal stages.

OD: over-drain; the drainage water from green-house media slabs that can be collected formeasurement, analysis and re-circulation.

PAR: photosynthetically active or photoactiveradiation; the range of the light spectrum(400-700 nm) that can be used by plants inphotosynthesis; expressed as microeinsteinsper m2.

parasite: an organism that derives its foodfrom the body of another organism, the host,without killing the host directly, e.g. mos-quito; also an insect that spends its immaturestages in the body of a host that dies justbefore the parasite emerges, this type is alsocalled a ‘parasitoid’ and is commonly used inbiocontrol progams.

parthenocarpy: fruit development withoutfertilization of the flower; parthenocarpicfruit is seedless and generally smaller and ofpoor quality compared to seeded fruit.

P band: the range of temperatures over whichthe greenhouse vents open.

pedicel: the stalk of one flower or fruit in acluster.

peduncle: the stalk of a cluster of flowers orfruits or of an individual flower or fruit if itis the only one in the inflorescence.

pesticide: any substance or mixture intendedfor preventing, destroying, repelling, killing,or controlling insects, rodents, weeds, nema-todes, fungi, or other pests; (any other sub-stance or mixture intended for use as a plantgrowth regulator, defoliant, or desiccant isalso classified as a pesticide under the PestControl Products Act).


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pesticide resistance: The genetically acquiredability of an organism to survive a pesticideat doses that once killed most individuals ofthe same population.

petiole: the stalk of a leaf that connects theblade to the stem of the plant.

pH: a logarithmic scale from 1 (very acid) to 14(very basic) used to express the acidity oralkalinity of a solution; most plants require anutrient solution between pH 5.5 & 7.5;greenhouse peppers do best in a solutionranging from 5.8 in the feed to 6.8 in thedrain water.

pheromone: a substance secreted by an organ-ism to affect the behavior or development ofother members of the same species; sexpheromones that attract the opposite sex formating are used to bait traps used in moni-toring or mass trapping of certain insects.

phloem: the food-conducting tissue of a plant,made up of sieve tubes, companion cells,phloem parenchyma, and fibers; it transportsthe products of photosynthesis from theleaves to all parts of the plant.

photosynthesis: the process by which plantcells make carbohydrates from carbon diox-ide and water in the presence of chlorophylland light and release oxygen as a byproduct.

physiological disorder: a disorder of plantscaused by factors other than pathogens; alsoknown as abiotic, non-parasitic, or non-pathogenic.

phytotoxicity: the ability of a material such asa pesticide, fertilizer or air pollutant to causeinjury to plants.

pistil: female part of the flower, usually con-sisting of ovules, ovary, style, and stigma.

pollinator: an agent of pollen transfer fromanther to stigma of the same or differentflowers; usually bees.

pollenizer: a cultivar or variety of a plant thatproduces compatible pollen that allows theflowers of another cultivar or variety to befertilized so they can produce fruit.

predator: any animal (including insects andmites) that kills other animals (prey) andfeeds on them.

PPM: parts-per-million; expression of concen-tration for very dilute solutions; often usedto describe the concentration of minorelements in a nutrient solution or pesticideresidues on a food product; 1 ppm = 1 gramin 1000 kilograms or 1 mL in 1000 L.

pupa (pl. pupae): The non-feeding stage fol-lowing the larva in insects with completemetamorphosis; during pupation, radicalstructural changes take place allowing for theemergence of the adult.

RH: relative humidity expressed as the watervapour in the air as a % of what it would beif the air was saturated at the same tempera-ture.

selective pesticide: a pesticide that is toxicprimarily to a narrow spectrum of insects,weeds, etc; leaving most other organisms,including natural enemies, unharmed; anto-nym of ‘broad spectrum’ pesticide.

sepals: the outermost flower parts making upthe calyx which usually encloses the petalsand other flower parts in the bud.

situ: on location; e.g. rockwool slabs in thegreenhouse rows.

slab: in greenhouse terminology, refers to therectangular bags of sawdust or rockwoolgrowing media.

stomate (pl. stomates or stomata): openings inthe epidermis of the plant, especially theleaves, that allows for diffusion of gases intoand out of the leaves; they are essential tothe operation of the transpiration stream thatdraws water and nutrients up from the roots.


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surfactant: a surface active compound thatlowers the surface tension of water, allowingpesticide droplets to spread out and covermore of the plant surface; may also be calledwetting agents or spreader-stickers.

systemic pesticide: a pesticide that has theability to be absorbed into the plant where itis carried in the xylem or phloem to variousparts; systemic insecticides are particularlyeffective against sucking insects, such asaphids, but they frequently have very longpre-harvest intervals when used on foodcrops.

transpiration: the process in which water andaccompanying nutrients are drawn up theplant; most of the water turns to vapour andis lost through the stomates; this processfeeds and cools the plant.

trap crop: a crop or portion of a crop intendedto attract pests so they can be controlled bytreating a relatively small area; or so the trapcrop and the pests can be destroyed togetherbefore the pests can reproduce and disperse.

vector: usually an insect, mite, fungus or nema-tode that acquires a virus from feeding on aninfected host and then transmits it when itstarts feeding on another host. The termapplies to both animal and plant diseases.

VPD: vapour pressure deficit; the differencebetween water vapour pressure in the leavesand in the greenhouse air expressed asgrams/m3.

W or WP: wettable powder pesticide formula-tion; older-type formulation that is difficultto measure and handle; largely replaced byflowable and soluble granule formulations.

xylem: that part of the plant’s vascular tissuethat conducts water and nutrients from theroots up through the plant in the transpira-tion stream.


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Bibliography

Adams, P. 1986. Mineral nutrition. pp. 281-334. InAtherton, J. G. and J. Rudich (eds.) The Tomatocrop: a scientific basis for improvement.Chapman and Hall, London and New York.

Andrews, J. 1995. Peppers: the domesticatedcapsicums. University of Texas Press, Aus-tin, Texas. p. 52-60.

Anonymous. 1952. The Yearbook of Agriculture:Insects. U.S. Dept. Agric., Washington, D.C.

Bakker, J.C. 1989. The effects of air humidityon growth and fruit production of sweetpepper (Capsicum annuum L.). J. Hort. Sci. 64(1): 41-46.

Bakker, J.C. 1989. The effects of temperatureon flowering, fruit set and development ofglasshouse sweet pepper (Capsicum annuum

L.). J. Hort. Sci. 64 (3): 313-320.

Bakker, J.C. 1991. Analysis of humidity effectson growth and production of glasshouse fruitvegetables. Doctoral dissertation, AgriculturalUniv., Wageningen, Netherlands. 155 pp.

Bakker, J.C., G.P.A. Bot, H. Challa and N.J. vande Braak (eds.). 1995. Greenhouse ClimateControl: an Integrated Approach.Wageningen Pers, Wageningen, Netherlands.279 pp.

Barendse, M. 1993. Extension/Tomato: Tem-perature is distributor of assimilates. InGroenten & Fruit, 3 (20): 21.

Barker, A.V. and H. A. Mills. 1980. Ammoniumand nitrate nutrition of Horticultural crops.In J. Janick (ed.) Horticultural Reviews, 2:395-423.

Blackman, R.L. and V.F. Eastop. 1984. Aphidson the World’s Crops: an Identification andInformation Guide. John Wiley & Sons, NewYork. 466 pp.

Dorais, M., S. Yelle and A. Gosselin. 1996.Influence of extended photoperiod onphotosynthate partitioning and export intomato and pepper plants. N.Z. J. Crop andHort. Sci. 24: 29-37.

Dreistadt, S.H. 2001. Fungus Gnats, ShoreFlies, Moth Flies, and March Flies.Univ.Calif., Agriculture and Natural Re-sources. Oakland. Publication 7448. 6 pp.

Gillespie, D., L. Shipp, D. Raworth, R. Foottit.2002. Aphis gossypii, Glover, Melon/Cottonaphid, Aulacorthum solani (Kaltenbach), Fox-glove aphid, Macrosiphum euphorbiae (Thomas),Potato aphid, Myzus persicae (Sulzer), GreenPeach aphid, (Homoptera: Aphididae), PP 44-49 in Mason, P., and J. Huber. BiologicalControl Programmes in Canada 1981-2000.CABI Publishing, New York.

Gorham, J.R., ed. 1991. Insect and Mite Pestsin Food: an Illustrated Key. U.S. Dept. Agric.Handbook 655. Washington, D.C.

Grange, R.I. 1985. Carbon partitioning inmature leaves of pepper: effects of daylength. J. Experimental Botany 36 (172):1749-1759.

Grange, R.I. 1987. Carbon partitioning inmature leaves of pepper: effects of transferto high or low irradiance. J. ExperimentalBotany 38 (186): 77-83.

Griffiths, D.A. 1999. Biological control of mites.In R. Albajes, M. Losovica Gullina, J.C. vanLenteren and Y. Elad (eds.), Integrated Pestand Disease Management in GreenhouseCrops, Kluwer Academic Publishers,Dordrecht, The Netherlands, p. 217-234.

Hanan, J.J. 1998. Greenhouses: advancedtechnology for protected horticulture. CRCPress, Boca Raton, Florida. 684 pp.


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Heuvelink, E. and L.F.M. Marcelis. 1996.Influence of assimilate supply on leaf forma-tion in pepper and tomato. J. Hort. Sci. 71(3): 405-414.

Khan, E.M. and H.C. Passam. 1992. Flowering,fruit set and development of the fruit andseed of sweet pepper (Capsicum annuum L.)cultivated under conditions of high ambienttemperature. J. Hort. Sci. 67 (2): 251-258.

McGreger, S.E. 1976. Bee Culture: insectpollination of cultivated crop plants. USDA,http://bee.airoot.com/beeculture/book/chap6/pepper.html

Moreshet, S., C. Yao, B. Aloni, L. Karni, M.Fuchs and C. Stanghellini. 1999. Environmen-tal factors affecting the cracking of green-house-grown bell pepper fruit. J. HorticulturalScience & Biotechnology 74 (1): 6-12.

Nederhoff, E.M. 1994. Effects of CO2 concen-

tration on photosynthesis, transpiration andproduction of greenhouse fruit vegetablecrops. Doctoral dissertation, Agric. Univ.,Wageningen, Netherlands, 213 pp.

Nederhoff, E.M. and J.A.M. van Uffelen. 1988.Effects of continuous and intermittentcarbon dioxide enrichment on fruit set andyield of sweet pepper (Capsicum annuum L.).Netherlands J. Agric. Sci. 36: 209-217.

Pressman, E., H. Moshlovitch, K. Rosenfeld,R. Shaked, B. Gamliel and B. Aloni. 1998.Influence of low night temperatures onsweet pepper flower quality and the effect ofrepeated pollinations with viable pollen onfruit setting. J. Horticultural Science &Biotechnology 73 (1): 131-136.

Rabinowitch, H.D., A. Fahn, Tal Meir and Y.Lensky. 1993. Flower and nectar attributesof pepper (Capsicum annuum L.) plants inrelation to their attractiveness to honeybees(Apis mellifera L.). Annals of Appl. Biol. 123:221-232.

Resh, H. M. 1997. Hydroponic Food Produc-tion: a Definitive Guidebook of SoillessFood-growing Methods, 5th ed. WoodbridgePress, Santa Barbara, California, 527 pp.

Rsabasse, J. M. and M.J. van Steenis. 1999.Biological control of aphids. In R. Albajes,M. Losovica Gullina, J.C. van Lenteren andY. Elad (eds.), Integrated Pest and DiseaseManagement in Greenhouse Crops, KluwerAcademic Publishers, Dordrecht, The Neth-erlands, p. 235-243.

Rylski, I. 1986. Pepper (Capsicum). In S.P.Monselise (ed.), Handbook of Fruit Set andDevelopment. CRC Press, Boca Raton,Florida , p. 341-354.

Smith, D. 1996. Grower Manual 2: Growing inRockwool. Nexus Media Limited, Swanley,Kent, UK, 138 pp.

Stanghellini, C. 1988. Microclimate and transpi-ration of greenhouse crops. ActaHorticulturae 229: 405-410.

Stanghellini, C. and W. T. van Meurs. 1992.Environmental control of greenhouse croptranspiration. J. Agric. Engineering Research51: 297-311.

Turner, A.D. and H.C. Wien. 1994. Dry matterassimilation and partitioning in peppercultivars differing in susceptibility to stress-induced bud and flower abscission. Annalsof Botany 73: 617-622.

UC-IPM. 2001. Integrated Pest Managementfor Floriculture and Nurseries. Publication3402 Univ. Calif. Agriculture and NaturalResources, Oakland. 422 pp.

Winsor, G. and P. Adams. 1987. Diagnosis ofMineral Disorders in Plants, Volume 3:Glasshouse Crops. Her Majesty’s StationeryOffice, London. 168 pp.


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Useful Publications

General

A Guide to Starting a New Farm Enterprise

–BCMAFF – available online at http://www.agf.gov.bc.ca/scregion/index.htm

B.C. Trickle Irrigation Manual 1999 –$30.00 – available at Irrigation Industry Asso-ciation of B.C., 2330 Woodstock Dr.,Abbotsford, B.C. V3G 2E5. Phone 604-859-8222. Also online at http://www.agf.gov.bc.ca/resmgmt/publist/500series/565000%2D1.pdf

Business Management Online: A Business

Planning Directory & Resource Guide –

2002 – available online at http://www.agf.gov.bc.ca/busmgmt/

Environmental Farm Planning Reference

Guide 2004 – available online at http://www.agf.gov.bc.ca/esrd.htm

Farm Management and Human Resources

– assorted factsheets – available online athttp://www.agf.gov.bc.ca/indcomp/bus_mgmt.htm

Lower Mainland Horticultural Improve-

ment Association Short Course Proceed-

ings – limited quantities of back issues areavailable at the Abbotsford Agriculture Centre,1767 Angus Campbell Rd., Abbotsford, B.C.V3G 2M3. Phone 604-556-3001

Greenhouse

An Overview of the B.C. Greenhouse Veg-

etable Industry 2003 – BCMAFF – availableat http://www.agf.gov.bc.ca/ghvegetable/publications/documents/industry_profile.pdf

B.C. Greenhouse Vegetable Production

Statistics – available online at http://www.agf.gov.bc.ca/stats/greenhouseveg/42.htm

Business Planning Guide – Greenhouse

Vegetable 1992 – available online at http://www.agf.gov.bc.ca/busmgmt/bus_guides/green_guide.htm

Greenhouse Climate Control – An Inte-

grated Approach. – Bakker, J.C. et al. 1995.Wageningen Pers, Wageningen, Netherlands.279 pp.

Greenhouse Equipment Suppliers and

Contractors 2003 – available online at http://www.agf.gov.bc.ca/resmgmt/publist/300se-ries/334200-3.pdf

Greenhouse Heating Requirements 1983 –available online at http://www.agf.gov.bc.ca/resmgmt/publist/300series/334230-1.pdf

Greenhouse Pepper – Planning for Profit

Sheets 2001 – available at Abbotsford Agricul-ture Centre, 1767 Angus Campbell Rd.,Abbotsford, B.C. V3G 2M3

Greenhouse Vegetable Production Guide

for Commercial Growers 1996/97 – out ofprint – limited number of pages may be photo-copied at Abbotsford Agriculture Centre

Greenhouse Ventilation 1990 – availableonline at http://www.agf.gov.bc.ca/resmgmt/publist/300series/306445-1.pdf

InfoBasket –portal to agri-food information

on the net – Greenhouse Vegetable 2004

www.infobasket.gov.bc.ca

Irrigation Water Quality for B.C. Green-

houses 1996 – available online at http://www.agf.gov.bc.ca/ornamentals/floriculture/irrwater.pdf


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Strengthening Farming – Right to Farm –

Farm Practices, Greenhouses 2004 – avail-able online at http://www.agf.gov.bc.ca/resmgmt/fppa/refguide/commodity/870218-17_Greenhouse.pdf

Treatment of Greenhouse Recirculation

Water and Bio-Sand Fitration 1999 – avail-able online at http://www.agf.gov.bc.ca/resmgmt/publist/500series/512000-2.pdf

Tuning Your Heating System for Maximum

Efficiency 1985 – available online at http://www.agf.gov.bc.ca/resmgmt/publist/300se-ries/306220-1.pdf

Understanding Humidity Control In Green-

houses – available online at http://www.agf.gov.bc.ca/ornamentals/floriculture/humidity.pdf

Pest and Disease Control

A World-wide Guide to Beneficial Animals,

Insects, Mites, and Nematodes used for

Pest Control Purposes. Thompson Publica-tions. PO Box 9335, Fresno, CA 93792.Ph.209-435-2163, Fax.209-435-8319

Biological Control Agent Catalogue.Terralink Horticulture Inc. 464 Riverside Rd.,Abbotsford, BC V2S 7M1. Ph.604-864-9044;1-800-661-4559; Fax.604-864-8418. website:www.terralink-horticulture.com

Biological Control – Protected Crops.Desmond Day. 1991. Grower Digest #11.Grower Books Ltd., 50 Doughty St., LondonWC1N2LS

Biological Technical Manual. Applied Bio-nomics Ltd. / Evergro-Westgro Canada Inc.7430 Hopcott Way, Delta, B.C. V4G 1B6.Ph.604-940-0290; 1-800-663-2552, Fax.604-940-0269. Website: www.growercentral.com

Compendium of Pepper Diseases. Pernezny,K.L. et al. 2003. APS Press. 3340 Pilot KnobRd., St. Paul, MN 55121-2097, USA Ph.1-800-328-7560. 88pp.

Compendium of Tomato Diseases. Jones,J.B. et al. 1991. APS Press. 3340 Pilot KnobRd., St. Paul, MN 55121-2097, USA Ph.1-800-328-7560. 100pp.

Diagnosis of Mineral Disorders in Plants

V.3: Glasshouse Crops. Winsor, G. and P.Adams. 1987. HMSO, London. 168pp.

Diseases and Pests of Vegetable Crops in

Canada. Howard, R.J. et al. 1994. Entomologi-cal Society of Canada. 393 Winston Ave.,Ottawa, Ontario K2A 1Y8. 554pp.

Greenhouse Vegetable – Crop Cleanup

1997. available online at http://www.agf.gov.bc.ca/cropprot/cleanup.htm

Handbook for Pesticide Applicators and

Dispensers. B.C. Ministry of Water, Land andAir Protection, Pesticide Management, 10470 –152 St., Surrey, B.C. Ph.604-582-5200

Integrated Control of Greenhouse Pests for

Commercial Growers. BCMAFF. 1992.

Abbotsford Agriculture Centre, 1767 AngusCampbell Rd. Abbotsford, B.C. V3G 2M3.Ph.604-556-3001.

Management of Powdery Mildew,

Leveillula taurica, in greenhouse peppers.

2004 – available online at http://www.agf.gov.bc.ca/cropprot/peppermildew.htm

Managing Diseases in Greenhouse Crops.

Jarvis, W.R. 1992. APS Press. 3340 Pilot KnobRd., St. Paul, MN 55121-2097, USA Ph.1-800-328-7560. 288pp.

The Biology of Glasshouse Pests and Their

Natural Enemies – Knowing and Recogniz-

ing. Malais, M and W.J. Ravensberg. KoppertBiologicals.


9. GROWER BIO-CONTROL & SPRAY RECORDG

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Initials

R

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R

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Index

Symbols

2,4-D 1303 to 4-stem system 50

A

A. colemani 82a.i 170abamectin 107active climate 22active ingredient 170acute toxicity 170adjuvant 170ADT 17ADT 17, 170adventitious 170Aerosol Generators 155air pollution 31Amblyseius cucumeris 77, 99, 104Amblyseius degenerans 104ammonium bifluoride 132anion 170anthers 170anti-sapstain 44Aphelinus abdominalis 77, 82, 89Aphid Life Cycle 80Aphidius 99Aphidius ervi 89Aphidius matricariae 82Aphidius spp 77Aphidoletes 82, 89Aphidoletes aphidimyza 77Aphids 80Aphis gossypii 80Applying Pesticides 144Approximate Quantities to Use In Backpack Sprayers

161Aulacorthum solani 80average daily (24 hours) temperature 17Avid 107

B

Bacillus thuringiensis var. kurstaki 94Bacillus thuringiensis var. israeliensis 91Bacterial Soft Rot 121Bactericera cockerelli 97Banvel 130bar 170Bees and Beneficial Insects 146Bemisia tabaci 107BER 5, 40, 52, 61, 67, 125, 170

bicarbonate 61biocontrol agents used in aphid control 82Biological Control 76, 170blossom end rot 5, 125Blue sticky traps 75boost 18Boron 38Botrytis cinerea 117Bradysia spp 90brodifacoum 111bromadiolone 111Btk 94

C

cabbage looper 92calyx 170canopy 170capacitive meter 22captan 114, 119Carbon Dioxide 27Carbon monoxide 32carmine mite 101cat-facing 170caterpillar 170cation 170chelate 170Chemcial and Biological Crop Protection 135Chemical Control 78Chemprocide 118Chlorination 121chlorophacinone 110, 111chlorosis 170chronic toxicity 170

CO 32CO

2 1

CO2 enrichment 27

coco-fibre 44compatibility 170Compressed Air 155condensation 26Confirm 94contact pesticide 170cornicles 170cotton/melon aphid 80Crop Cleanup 130Cultural Control 76Cuticle Cracking 127


D

D 170Damping-Off 113Day storage 38DDAC 132dead zone 20, 170Delphastus pusillus 108dew point 23, 171DF 171Diapause 101diapause 78, 171Diazinon 89Dibrom 90, 94, 96, 98, 99, 107, 108Dicyphus hesperus 93, 104Dipel 94diphacinone 110, 111Disposal of Containers 145Disposal of Unwanted Pesticides 145drench 171Dyno-mite 107

E

EC 3, 39, 171Echinothrips americana 98ectoparasite 171electrical conductivity 39Electrostatic Sprayers 155Embedded 22Emergency Response 146emulsifiable concentrate (EC) 171Encarsia formosa 77, 108endoparasite 171endosulfan 90, 96entomophagous nematodes 171Eretmocerus spp 108ergocalciferol 111Erwinia carotovora 121ethylene 31

F

F 171FALL PRODUCTION 70feeding formulas 38Field Mice 110Fires 146First Aid 139Fish and Other Wildlife 146Fisheries Act and Migratory Birds Regulations 135fixed screens 21flue gases 27foam 44fog 21Food and Drugs Act 135Foray 94

Foxglove aphid 80, 88Frankliniella occidentalis 98Fruit abortion 6Fruit Spots 128fumigation 171fungus gnats 49, 90Fusarium 48, 91Fusarium Stem and Fruit Rot 115

G

G 171global radiation 15glyphosate 129Gramoxone 130green peach aphid 80, 88Greenhouse Cleanup 78, 129Greenhouse Pesticide Equipment 154greenhouse whitefly 107grey mould 117grow pipe 19Growth Cracks 127

H

Harvesting Restrictions 145Hazard Shapes and Symbols 139High Pressure Pesticide Applicator 155High-Volume Sprayers 152honeydew 81, 97, 171Horticultural training ivhost 171household bleach 129humidity 22hydrogen peroxide 132hygrometer 22hyper-parasite 171hyperparasitoids 82Hypoaspis spp 77, 91, 99, 131

I

imidacloprid 89Impower 89infrared gas analyzer 30infrared thermometers 22inoculum 171instar 171Internal Growths and Wings 127IPM 75, 171IRGA 30, 171irrigation 33

K

Kipp solarimeter 15knots 127


L

L or LC 171LAI 171larva (pl. larvae) 171LD

50 171

Leaf area index 2Leveillula taurica 119Light Traps 94Liquid CO

2 27

Low-Volume Sprayers 152Lysol 129

M

Macrosiphum euphorbiae 80Maestro 114Manganese 38manganese 44manometer 30maximum residue limits 135MCPA 130MDLA 22Melon/cotton aphid 88Mice 110microbial pesticide 172micromolar (mmol) solution 163Microscopic Sulphur 120millimolar (mmol) solution 163Misshapen Fruit 127Mist Blower 154Mixing and Loading Pesticides 144molar solution 163molecular weight 172Monitoring 75monitoring 172moth flies 90moult 172MRL 135, 172mummy 172mycelium 172myclobutanil 120Mycostop 48, 114Myzus ornatus 80Myzus persicae 80

N

naled 90, 94, 96, 98, 99, 107, 108natural enemies 172necrosis 172nectary 172Nectria haematococca 115nematicide 172Netafim 131Nicotine Smoke 89, 99nitrogen oxides 32

No Damp 114Nova 120NOx 32nymph 172

O

OD 35, 172onion thrips 98Orius insidiosus 93Orius insidious 77Orius spp 104over-drain 33, 35oxine benzoate 114

P

P band 20, 172PAR 15, 172paraquat 130parasite 172Paratrioza cockerelli 97parthenocarpic 6parthenocarpy 172PCP Act 135pedicel 172peduncle 172Pepper Mild Mottle Virus 122pepper mottle virus 81perlite 44Personal and Environmental Safety Guidelines 143Pest Control Products Act & Regulations 135Pest Management Regulatory Agency 135Pest-in-First Method 103pesticide 172Pesticide Applicator Course for

Agricultural Producers 135Pesticide Control Act and Regulations 136Pesticide Poisoning 139pesticide resistance 173petiole 173pH 3, 173pheromone 173Pheromone traps 76, 93phloem 173photometric 15Photosynthesis 1physiological disorder 173Phytophythora 91Phytoseiulus persimilis 77, 102phytotoxic 129phytotoxicity 173pistil 173plant activation 26Plant Balance 10PMMV 122PMRA 135


Podisus maculiventris 95Poison Control Centre 139Poisoning and First Aid 139pollenizer 173Pollination 7pollinator 173potato aphid 80powdery mildew 119PPFD 15PPM 173pre-day 18pre-night 18predator 173Propagation 47Protective Clothing and Equipment 141Provincial Emergency Centre 146psychrometer 22Psyllids 97pumice 44pupa 173pyrethrin 90, 94, 98, 107, 108pyridaben 107Pythium 91, 113, 129

Q

Quality Control for Commercially Available Biologi 77

R

radiometric 15Rail pipe 19Rats 110Re-entry Restrictions 145Re-using Growing Media 132red squill 111Respiration 2RH 173Rhizoctonia solani 113rockwool 44roof sprinklers 21Root-dieback 4Roundup 129

S

Safer’s Insecticidal Soap 89, 94, 98, 107, 108Sanitation 129Sanmite 107sawdust 44Sclerotinia sclerotiorum 120Seed germination 48selective pesticide 173sepals 173shore flies 90simazine 130situ 173

skim milk powder 123slab 173Smoke Fumigators 155sooty 97sooty mould 81, 97, 108Special Environmental Precautions 146Spills 146spined soldier bug 95spray nozzles 156Sprayer Basics 152Sprayer Calibration 157Sprayer Components 155Spraying Equipment 152SPRING PRODUCTION 59SPRING-SUMMER PRODUCTION 64Steam Sterilization of Rockwool Slabs 133Stink bugs 95stomate 173Storing Pesticides & Shelf Life 143Streptomyces griseoviridis 114sulfaquinoxaline 111sunscald 1, 60, 126surfactant 174sweet potato whitefly 107systemic pesticide 174

T

Tails 127Tamarixia triozae 97tebufenozide 94Tetranychus cinnabarinus 101Tetranychus urticae 101Thermal Fogging Machines 154thermistors 22Thiodan 90, 96Thiram 114Thrips 98Thrips fuscipennis 98Thrips tabaci 98Time of seeding 48ToMV 123TMV 123tobacco mosaic virus 123, 129tobacco mottle virus 81tobacco ringspot virus 81tobacco wilt virus 81Tomato Mosaic Virus 123tomato spotted wilt virus 99transpiration 4, 33, 174Transportation of Dangerous Goods Act 135trap crop 174Trialeurodes vaporariorum 107Trichogramma 93Trichoplusia ni 92trisodium phosphate 47, 123


Trounce 90, 94, 98, 107, 108TSP 47Two-spotted Spider Mite 101two-stem system 50

V

vapour pressure deficit 4VectoBac 91vector 174violet aphid 80Virkon 47, 118, 129, 131Voles 110VPD 4, 22, 174

W

W or WP 174warfarin 111water quality 42WCB regulations 136Weed Control 129western flower thrips 98western red cedar 44white mould 120Whitefly 107whitewash 21WINTER PRODUCTION 53Workers’ Compensation Board 136

X

xylem 174

Y

Yellow cedar 44Yellow sticky traps 75

Z

zinc phosphide 110, 111

ministry of agriculture, food and fisheries

Documents