plant disease & control_ [compatibility mode]

8/8/2019 Plant Disease & Control_ [Compatibility Mode]

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Plant Disease and ControlIntroduction to

Abdul HafeezPlant PathologistDepartment of Agriculture Azad Kashmir


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DiseaseDisease

Series of responsesSeries of responses

abnormalityabnormality

lossloss

microorganismsmicroorganisms EnvironmentalEnvironmental factorsfactors

morphologymorphology

physiophysiollogyogy

quantquant ityity

qualiqualityty

PLANT DISEASE ?PLANT DISEASE ?

WHAT ISWHAT IS

(shape)

(function)


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Symptoms

The external & internal alterationsof a plant as a result of a disease


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Primary SymptomsDirect changes of tissues infected by

pathogen

leaf spot


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Secondary Symptoms

Indirect & subsequent changes of a distance

Sclerotium w ilt

from the site of the pathogen


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Localized symptoms

(in a particular part of the plant)

leaf blight

(death of cells in restricted areas)

(death of cells: not restricted)

leaf spot

bacterial canker


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(Death of cells and tissues)

dry rot: fungi

Rots

soft rot: bacteria

anthracnose


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Hypertrophy & Hyperplasia

root knot (gall)

(overgrowth of tissue)


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Systemic symptoms

(spreading throughout the plant body)


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Transformation of tissues/ organs

phyllody


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Stunting/Dwarfing

(Reduced Growth)

Leaf roll / leaf curl

Dwarf


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Changes in colorationChanges in coloration

phosphorus deficiencyphosphorus deficiency

white leaf of sugarcanewhite leaf of sugarcane

mosaic


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Symptoms with SignsSymptoms with Signs

rustrust


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smutsmut

Symptoms withSymptoms withSignsSigns


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downy mildew

powdery mildewpowdery mildew

Symptoms w ith SignsSymptoms w ith Signs


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Naming of DiseaseNaming of Disease

11.. With symptomWith symptom papayapapaya ringspotringspot

Watermelon fruit rotWatermelon fruit rot

22.. With signWith signrustrustsmutsmut

powdery mildewpowdery mildew


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1) Noninfectious/ abiotic agents- imbalance of nutrients

- extreme temperature/moisture

- Air & w ater pollutants, chemicals, etc.

2) Infectious / biotic agents

Fungi, bacteria, mollicutes,

viruses & viroids, nematodes,

protozoa

Causal agentsCausal agents


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Shapes & sizes of plant pathogens


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Fungi

bacteria

mollicutes

viruses

nematodes

viroids

protozoa

Parasitichigherplants


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DiseaseDiseaseTriangleTriangle

TiTi

meme

HostHost


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Disease CycleDisease Cycle

DisseminationDissemination

InfectionInfection

Monocyclic Disease

Polycyclic Disease

inoculationinoculation

SymptomSymptom

(1)

(2)(4)

(3)

developmentdevelopment

Reproduction

(5)


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Diagnostic TechniquesDiagnostic Techniques

1. Visual inspection of symptoms

2. Microscopic exam ination

3. Isolation for pure culture of pathogenand Identification of pure culture

4. Biochemical & physiological methods

5. Nucleic acid-based methods(molecular methods)


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disease

insect

Visual Inspection ofVisual Inspection ofSymptomsSymptoms

Determine : diseaseVS insect

insect


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Determine : biotic agentVS abiotic agent

abioticbiotic

Visual Inspection of SymptomsVisual Inspection of Symptoms


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Determine : Nutrient Deficiency VS Virus

virusnutrient deficiency



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Fungal Diseases


Use hand-lens/ microscope

- mycelium/ fruit ing body/

spores


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bacterial ooze

mass of bacterial cells

cut stem

from xylem

from cut leafspot

Bacterial Diseases


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Virus and Phytoplasma

virus

phytoplamainsect vector


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Transmission test

Indicator plant

Serology

Electron microscope

Nucleic Acid, DNA

Virus andVirus and PhytoplasmaPhytoplasma


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Nematode Damage

root knotroot knot

(gall)(gall)

Nematodes instained root

Symptom , Populat ion density in soil & root

poor growth


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Principles of Plant Disease Control

1. Reducing Initial Inoculum

2. Reducing Rate of Development


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Reducing Initial

InoculumExclusion - no introduction ofpathogen

Eradication-

eliminate pathogeninoculum

Therapy - eliminate pathogen from living host


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Reducing Rate of Development(To Slow Rate of Increase)

Host resistance - horizontal resistance

Protection - protect the host from infection

Avoidance - avoid contact of host and pathogenunder conditions favorable for

disease


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Reducing Rate of Development

AvoidanceAvoid putting host & pathogen in contact with

one another under a favorable environment

A. Geographic Selection

B. Site Selection

C. Environmental Management

D. Cultural Practices

Planting/Harvest dates Short season cultivars Cultivation practices, plant spacing Irrigation management, ferti l ity management


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Reducing Rate of Development

ProtectionA. Biological controlAntagonistic organisms (Streptomyces, Bacil lus,

Trichoderma, Paecil lomyces, Vertici l l ium)

Cross protection (inoculate mild strain to induceresistance for virulent strain of pathogen)

B. Chemical control

Protectant, Eradicant Contact, systemic pesticides

Fungicides, bactericides, nematicides


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Integrated P lantDisease Management

1. Manage the pathogen

2. Manage the host

3. Manage the environment


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Integrated P lant DiseaseManagement

1. Manage the pathogen

- Exclusion of inoculum

- Reduction of inoculum

- Eradication of inoculum


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Integrated P lant DiseaseManagement

2. Manage the host

- Induced resistance

- Breeding for disease resistance

- Protect ion


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Integrated P lant Disease

Management

3. Manage the environment

- Soil management

- Crop management

- Water management

plant disease & control_ [compatibility mode]

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