This document provides an overview of plant disorders and their diagnosis for urban foresters. It distinguishes between biotic disorders caused by living organisms and abiotic disorders caused by non-living factors. A systematic six-step process for diagnosis is outlined involving identifying the plant, examining patterns of abnormality, carefully examining the site, noting foliage characteristics, checking trunks and branches, and examining roots. Common signs and symptoms of disorders are defined, as well as types of stresses, abiotic disorders, biotic disorders, and how to seek additional information on diagnosis.
29. As you go through the process, try to eliminate certain possibilities… pH? pH!!! X X ??? ???
30. … and an opportunistic leaf spot. Poor tree health is rarely the result of one condition, but rather a complex [a combination of factors that lead to the stress of decline of a tree] of abiotic and biotic contributors. Stress this to the tree owner!
Not specific disorders but what to look for to be able to tell Best part of this class is to learn this process (nothing) What is a physiological disorder? however…
I cannot stress this enough. Take time to investigate! It’s my experience that most arborists/ horticulturists do NOT do this. When that’s completed you must make the appropriate recommendations.
Think like a non-arborist – like you know nothing about trees
I like to define my terms – in most cases this evening disease will mean the following: EPA’s experiment to test emissions from trees – wrongfully thought of as “pollutants.”
Following are a few slides of a disorder…can you guess what happened from these clues?
It’s more than just identification. Anyone know what this is?
You must know the species and everything about the plant. Think Michael Dirr!
Do comparisons with other plants on the site, especially of the same species. Look for differences in color or growth.
Often cross species lines – this can be a huge help
As we’ll discuss later, various foliar symptoms can give clues as to the disorder involved. Look at the location of the affected foliage as well. Leaves at the top of the tree that are affected usually indicate a vascular disruption. pH problems may appear only on one side.
The severity of trunk damage is almost always more than what is usually considered. ISA formula.
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Consumer confidence in the industry is poor. “Flip” diagnoses can make you look bad – who does the consumer trust? Usually, (unfortunately) someone on TV.
Example of borer holes vs. the causal factor. Questions on the diagnostic process?
Rust as a symptom
There can be many causes for a specific symptom. Ash rust. Don’t have a narrow focus.
Questions on signs and symptoms?
Barrel example
Insect defoliation, some herbicide damage, freeze damage
Heavy fruit production; most common causes of tree stress are site and/or environment related: inadequate water, extreme cold, adverse soil conditions – compaction, mechanical injury Stress is NOT irreversible. If the stress factor(s) can be identified, it is possible to alleviate the condition and improve the health of the tree. If only secondary facors are identfied and treated, the tree will likely continue to decline.
Stress may be reversible if you correctly identify the primary cause. Borer example. Questions on stress?
Book’s construction damage example; borers again
A reason not to over plant. Treatment: reduce competition.
Usually inhibition is minor and of importance on young plants. Most every plant has some capacity to produce an allelopathic reaction. Juglone. Tall fescue and other grasses have strong influence on young trees.
Treatments – remove the source or wash the foliage
Show sample of damage; odd curl or “cupping”, parallel venation; others may “bleach” leaf of chlorophyll (chlorosis). Soil sterilants will have long term effects. Apply herbicides according to label and keep them away from trees! Temperature effects.
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