Management of Avocado Pests in

California

28 May 2008

Joseph G. Morse

Professor of Entomology

University of California, Riverside, CA

• Prior to 1990, insects and mites on avocados in Californiawere under excellent biological control and rarely requiredchemical control

• Recent onslaught of invasive pests

– Persea mite (1990)

– Avocado thrips (1996)

– Diaprepes root weevil discovered in southern Californiain 2005 and is now close to commercial avocadoacreage

– Weevils, seed moth, and armored scales likely to beimported with Mexican fruit first allowed entry toCalifornia 1 February 2007

Scirtothrips perseae (Thysanoptera: Thripidae)

Avocado Thrips (July 1996)

Immatureavocadothrips feedingon fruit

$60 million crop loss due toavocado thrips in 2006

Context of Chemical Control Research withAvocado Pests

• Worldwide, few examples of good biological control of

pestiferous thrips species (chemical intervention is often

required)

• Scirtothrips citri (California citrus thrips)

• Scirtothrips aurantii (South African citrus thrips)

• Scirtothrips dorsalis (Chili thrips or yellow tea thrips)

Avocado Thrips, Scirtothrips perseae

• ABAMECTIN - Agri-Mek 0.15 EC

• Abamectin relatively slow in killing avocadothrips

• Quite persistent in leaves, with controlpersisting 6-10 weeks or more (increases thepotential for resistance)

• Also effective in suppressing persea mitepopulations

Standard control method for Avocado thrips:

Oligonychus perseae (Acari: Tetranychidae)

Persea Mite

Female

Male

“Nests” of avocado persea mite

Leaf drop observed with highpersea mite levels

www.ipm.ucdavis.edu

Example

Photo ID

Sheet

Resistance Management on Avocados

FujiMite

Envidor

Zeal

Persea mite

Danitol

Veratran D

Delegate

Agri-Mek

Avocadothrips

21

23

10B

3

Near 3

5

6

IRACclass

Electron transportinhibitor

Ketoenole

Phenetole

Pyrethroid

Plant alkaloids (2)

Spinosyn

Avermectin

Class of chemistry

2012?

2010?

Registration 2009?

Registration 2009?

Registered (Good forrotation)

Registered (Cross resistancepotential to Agri-Mek?)

Registered

Registration status

IRAC = Insecticide Resistance Action Committee (http://www.irac-online.org/)

Steep Hillsides Are A Formidable ChallengeFor Effective Pesticide Application

Pesticide Application onCalifornia Avocados

!More than 90% of avocados are on steep hillsides

with a drive row every 4 rows

!Most sprays are applied by helicopter (468-936 l/ha)

!$ 124 - 247 per ha just for application costs

Hand Spraying With Drag Hoses

! Ca. $2500 for a small spray tank and drag hose pulled

behind a truck or ATV (all terrain vehicle) on drive rows

!91 m or longer drag hose

!570 liter or larger tank

!Treatment at 2800-4675 liters per ha

!Benefits -- excellent coverage and timing possible;

possibility of spot treatments

!Problems -- labor can be expensive and treatment difficult

on steep hillsides

Another option for pesticide application-- trunk injection (research in progress)

The Trunk Injection Process (ArborJet, Inc.)

Drill throughto the xylem

Tap in anArborplug® (#useddepends ontrunk diam.)

Inject ameasureddose ofinsecticide

Injectioncomplete

ResidueAnalysis ByELISA

ToxicityAssessed ByBioassay

LeavesSampled FromTreated Trees

Trunk Injections

• Acephate and Dinotefuran uptake was very rapidcompared with imidacloprid

• Imidacloprid mobilization within the xylem wasmost active when the Spring flush occurred

• Insufficient data at present to determine howeffective treatments will be against avocado thrips

Preliminary Conclusions (Research in Progress)

Mexican fruit first allowed entry inCalifornia 1 February 2007

Interceptions of armored scales

(Diaspididae) on Mexican Hass

avocados entering California

Armored Scales Entering CA from Mexico

• Sampled 1 carton per truck from 102 trucks that entered CAover 20 Sept 2007 - 1 Jan 2008

• Seven species of scale found, 6 not present in California

• Most common scale was Abgrallaspis n. sp.

• Abgrallaspis sp. found (live + dead) in 89 of 102 cartons(87%)

• Live Abgrallaspis sp. eggs or crawlers found in 42 cartons(41%)

Management of Pests on California Citrus

28 May 2008

Joseph G. Morse

Professor of Entomology

University of California, Riverside

Citrus Growing

Regions in California

Ca. 70% of

current citrus

acreage is in the

San Joaquin

Valley

California Citrus Pest Management

"Pest problems vary a good deal by growing region

"Fruit are grown for the fresh fruit market (juice isnot profitable in California) so cosmetic standardsare high

"Most packinghouses now use high-pressurewashers to remove scales and sooty mold fromfruit

California Citrus Pest Management

San Joaquin Valley - 70% of the state’s citrus

1. Monitor for Citrus Thrips in spring with treatments applied as needed

Delegate (spinetoram) is replacing Success (spinosad) - more effective and

persistent but same class of chemistry (resistance concerns)

2. Red Scale controlled in alternate years with Esteem (pryiproxyfen)

Esteem is very effective but cottony cushion scale outbreaks were seen

during the first 2 years of use (sterilization of vedalia beetle)

Citrus Thrips, Scirtothrips citri

(Thysanoptera: Thripidae)

– Native to southwestern U.S. and northwestern

Mexico - Citrus is the exotic species

Thrips scarring of fruit

Wingless thrips nymphs

Winged, adult citrus thrips

Wingless, 1st and 2nd instar thrips Predatory mite feeding on a thrips

California red scale,Aonidiella aurantti

(Diaspididae)

Resistance toorganophosphates andcarbamates appeared inthe 1990’s

Biological control programintroduced in 1992

14 releases, 1 every 2weeks over 15 Feb - 15Sept (247,100 total per haper year; cost of $222/ha)

California Red Scale

Pheromone trapfor monitoring

Adult male scale

Male scale inseminating a third

instar female

Aphytis female penetrating the grey skirt

of a young female to deposit an egg

Aphytis melinus are sold in plastic cups with honey on the lid

Release wasps by tapping cup at every 6th tree in every 6th row

Aphytis egg on 3rd instar scale body

Aphytis melinus larva feeding on anearly third instar red scale

Scale cover and Aphytis remains

Early in the evolution

of resistance

A B

Concentration

Pro

port

ion o

f popula

tion

Resistant individualsResistant individuals

at low numbersat low numbers

Fitness of resistantFitness of resistant

individuals is importantindividuals is important

SeleçãoSeleção

Concentration

A BPro

port

ion o

f popula

tion

Selection(= pesticides sprays)

Concentration

A B

Distribution

after

resistance has

evolved

Pro

port

ion o

f popula

tion

California red scale uses esterase enzymes

to resist organophosphates and carbamates.

Esterase enzyme activity correlates with

resistance.

Fresno

Visalia

Sanger

Orosi

Lindcove

Lindsay

Strathmore

Porterville

Richgrove

Edison

Bakersfield

Tulare

Delano

Hanford

Orange CoveHwy 99

Hwy 5

Hwy 65

High Resistance

Low Resistance

Susceptible

Kern Co.

Tulare Co.

Fresno Co.

Populations of

California Red

Scale

Resistant to

Organophosphate

Insecticides

(1993-1997)

California Citrus Pest Management

New pest species could severely upset pest managementpractices

Diaprepes root weevil - unclear if soil temperature will be toohigh in interior regions allowing it to become a seriousproblem

Asian citrus psyllid - serious vector of HLB (yellow shootdisease) and present in the nearby Sonora region of Mexico

8-18 sprays per year being used by Florida citrus growers toreduce psyllid populations

Not clear if citrus production in Florida will survive - levels ofHuanglongbing (HLB) appear to be increasing

Sources of Information -- California Citrus Arthropod Pest Management

• Integrated Pest Management for Citrus (3rd Ed., late 2008) Univ. of Calif. (UC)

DANR Publication # 3303 (www.ipm.ucdavis.edu)

• UC Pest Management Guidelines on the web

– www.ipm.ucdavis.edu - select “Pest Management Guidelines”, “Citrus”,

and the pest of interest

– Basic biology, monitoring methods, treatment thresholds, UC

recommended treatments, precautions in using pesticides (bees,

selectivity)

• Other UC IPM Publications

– IPM in Practice: Principles and Methods of Integrated Pest Management

– Managing Insects and Mites with Spray Oils, Publication # 3418