Chapter 32 - Foliar, Flower, and Fruit Pathogens

Abstract

This chapter introduces some of the antagonists of plant pathogens as representative of the broad taxa and presents some methods by which these beneficial organisms can be employed in limiting plant diseases. Stem diseases produce symptoms that include decay and cankers on forest and orchard trees and wilts such as Dutch elm disease and chestnut blight Barr of Asian origin infecting the American chestnut, Castanea dentata. Flowers are ephemeral structures and have limited opportunity to become infected. One major disease of flowers that has received attention is fire blight of rosaceous plants, caused by the bacterium Erwinia amylovora. In order to understand the principles that apply to biological control of plant pathogens, it is required to consider the ecology of the system at the level of the pathogens and the agents used to control them. Aerial plant surfaces, by and large, present hostile environments to colonizing microbes. The pathogenic microbes attempting to colonize these surfaces may face a number of difficulties, including competition with other nonpathogenic microbes. Microbial competition can be important at two main stages of growth of the pathogen populations. First, there may be competition during the initial establishment on a fresh resource that was not previously colonized by microorganisms. Second, after the initial establishment, there is further competition to secure enough of the limited resources present to permit survival and eventual reproduction.