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Deciphering Diagnostics
Plant Pathology …
… the study plant diseases and disorders
PURPOSE:
learn how living and non-living factors can contribute or lead to plant disease AND how to differentiate between them
DISEASE (biotic)impairment of the normal state of a plant, that interrupts or
modifies its ability to function normally
PATHOGEN/DISEASE AGENTorganism that causes the disease process within a host plant
DISORDER (abiotic)a non-pathological disruption, within the host, that affects the
functioning of the plant’s system
SYMPTOMvisible reaction by plant to pathogen
SIGNpathogen or its parts are visible on plant
TERMS TO KNOW
galls
wilts cankers
blights
leaf spots
molds & mildews
crown rotsroot
rots
egg laying
leaf mining
SUB … terranean
stippling
rasping or scratching
chewing
HOW INSECTS & DISEASE IMPACT THE LANDSCAPE
boring
How Diseases Affect Plant Functions
Root rots interfere with water and nutrient
absorption
Stem infections interfere with water and nutrient movement and support
Leaf spots, blights, molds and mildews interfere with photosynthesis
Fruit infections interfere with storage of foods
Athlete’s Foot
SkinDiseases
FoliageDiseases
Root Diseases
Heart Disease
Vascular System Disease
- Dutch Elm -
Disease Triangledisease is dependent on three components:
Pathogen
Disease
Diagnosing in the
Landscape
… and surviving
What’s the problem?
CULTURAL … improper planting methods, overwatering, etc.MECHANICAL … mower/trimmer injury
ANIMALS - dogs, deer, rodents, woodpeckers, etc.ENVIRONMENTAL - weather related factors
INSECTS/MITES - beetles, caterpillars, spider mites, etc.DISEASES - fungal, bacterial, viral, etc.
Abiotic (non-living) Agents
excessive moisturedrought
freeze injurypesticides
high soluble saltsair pollutants
nutrient imbalancepH
Biotic (living) Agents
fungibacteriaviruses
phytoplasmaparasitic nematodes
parasitic plantsinsects
Ask Questions!What is the plant?
What do you see (symptoms and signs)?New planting or is it established?
Planted properly?Right plant in the right place?
Current and/or past weather conditions?Appearance when healthy?
How should the plant appear at current time?
Disease Symptoms visible reaction by plant to pathogen
leaf spots chlorosis / necrosis tip dieback
cankers gallsrotted roots
Disease Signs pathogen or its parts are visible on plant
spores conks
myceliummushrooms bacterial ooze
Insect/Mite Symptoms how the insect or its presence affects/injures the plant
leaf feeding injury
oviposition scars
leaf galls
chewing injury on twig
branch/twig dieback
stippling
leaf mines
exit holes
Insect/Mite Signs where the pest (or part of the pest) is visible
live adults
immatures
pupa case
eggs webbing
frass
honeydew sooty mold cast skins
deformed or odd growth
habit
abiotic disorders
drought stress
bark splitting freeze injury
sunscald
girdling roots
Identifying insects in the landscape is a learnable skill, that gets easier with practice!
https://www.ag.tennessee.edu/spp/Pages/default.aspx
https://www.facebook.com/SoilPlantPestCenter
know host plant - recognize damage - process of elimination
Amy DismukesWilliamson Co.
and
David CookDavidson Co.
