Concepts and Definitions

Abstract

Oral inquisitions, required of those who aspire to advanced degrees in plant pathology, often begin with a request for the candidate’s definition or concept of plant disease. After a struggle, the candidate extracts from a brain freshly crammed with scientific names of pathogens, disease cycles, biochemical pathways, and a variety of other disorganized information, a definition memorized in some introductory course. Usually this definition attempts to distinguish normal or healthy plants from abnormal or diseased ones. This leads to a discussion of the meaning of the term “normal” and to the conclusion that, by the candidate’s definition, plants which produce five times the average yield for a given locality must be diseased.