Diagnosing Plant Damage - Damaged Garden Plants

INTRODUCTION

To determine what factors damaged a plant requires an inquisitive, investigative approach combined with careful observation and the ability to put all the pieces together to reconstruct the event(s) that produced the plant damage. Accurate diagnosis must be made before corrective action can be taken; even if no corrective measures are available, there is satisfaction in simply knowing what the problem is and what its future development might be.
Probability of correct diagnosis based on only one or two clues or symptoms is low. Similarities of symptoms produced on the same plant by completely different factors frequently make the use of symptoms alone inadequate.
In diagnosing plant damage a series of deductive steps can be followed to gather information and clues from the big, general situation down to the specific, individual plant or plant part. Through this systematic, diagnostic process of deduction and elimination, the most probable cause of the plant damage can be determined. Steps to follow in gathering diagnostic information are presented in Table 1. Each step will then be expanded and guidelines presented as we proceed through the diagnostic process. We will first identify the problem, then attempt to distinguish between living and nonliving damaging factors based on the observed damage patterns, development of the patterns with time, and other diagnostic signs. Factors causing plant damage can be grouped into two major categories:
Living factors: living organisms such as pathogens (fungi, bacteria, viruses, nematodes) and pests (insects, mites, mollusks, rodents...). With living factors, "Something is missing, and something is gained."
Nonliving factors: mechanical factors (i.e. breakage, abrasions, etc.); physical, environmental factors (extremes of temperature, light, moisture, oxygen, lightning); and, chemical factors (chemical phytotoxicities, nutritional disorders, etc.).

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