Plant PathologyPlant Pathology

David R. Drake

PathologyPathology

The study of disease.

DiseaseAnything that causes abnormal

growth

Plant DiseasePlant Disease

Any disturbance of a plant that interferes with its normal growth and development, economic value, and aesthetic quality;

a continuously, often progressively affected condition in contrast to injury, which results from momentary damage.

Source: Plant Diseases: Their Biology and Social Impact. Gail L. Schumann APS Press

Historical Plant DiseasesHistorical Plant Diseases

Irish Potato FamineAmerican Chestnut BlightDutch Elm Disease.St. Anthony’s Fire Tulip Virus

St. Anthony’s FireSt. Anthony’s Fire

ErgotPrevalent in Rye

Tulip VirusTulip Virus

Tulips introduced to Europe circa 1550Virus infected bulbs created Tulipmania

from 1634-37.

PRICE BARTERED FOR 1 BULBPRICE BARTERED FOR 1 BULB

4 Tons Wheat 8 Tons Rye 4 Fat Oxen 8 Fat Pigs 12 Fat Sheep 2 Hogsheads Wine

4 Barrels Beer 2 Barrels Butter 1000 Lbs Cheese 1 Bed with Accessories 1 Full-dress Suit 1 Silver Goblet

Types of PathogensTypes of Pathogens

ParasiticNon-parasitic (abiotic)

Pathogen

Host

Environment

Factors in Disease:Factors in Disease:Disease TriangleDisease Triangle

ParasiticParasitic

FungiBacteriaVirusNematodesprotoplasmaParasitic plants

FungiFungi

Lack cholorphyll100,100 – beneficialMost microscopicSporesFungicides

BacteriaBacteria

Single-celledBinary fissionRapid multiplicationFree moistureBactericides

VirusVirus

Protein and nucleic acidSub-microscopicInsect vectoredMechanical transmission

NematodesNematodes

Microscopic eel wormsEggsStyletVirus vectorsNematicide

ProtoplasmaProtoplasma(mycoplasma)(mycoplasma)

Similar to bacteriaNo cell wallVectored by leafhoppersControlled with antibiotics

Parasitic PlantsParasitic Plants

Dodder

Non-parasiticNon-parasitic

Iron chlorosisPowdery mildewCytosporaFire blight

Iron Chlorosis

Powdery MildewPowdery Mildew

Halt (thiophanate methyl)BenlateFunginexBayletonSulfurTilt

FunginexFunginex

Roses– Powdery mildew– Rust (rare)

Fruit– Powdery mildew– Brown rot (rare)

CytosporaCanker

Fire Blight

Fire Blight ControlFire Blight Control

Avoid excess nitrogenPrune out cankersTreat with fixed copper or streptomycin

CuitlachocheCuitlachoche

Safflower oil Onion chopped Garlic chopped Chilies Cuitalchoche

3T

2T

2

4

4 Cups

Saute’ until translucent

Verticillium Wilt

ChlorothalonilChlorothalonil

Disease control with DaconilDaconil lawn and garden fungicideDaconil 2787Multi-purpose fungicide

White Mold

Slime FluxWet Wood