Biological Control Agents for Plant Pathogens

Biological control of plant pathogens is fundamentally a matter of ecological management of a community of organisms, as is all biological control. In the case of plant pathogens, however, there are two distinctions from biological control of organisms such as insects and plants. First, the ecological management occurs at the microbial level, typically in microcosms of the ecosystem such as leaf and root surfaces (Andrews 1992). Second, biological control agents include competitors, as well as parasites. While hyperparasites of plant pathogens and natural enemies of nematodes function in much the same way as do natural enemies (parasitoids) in arthropod systems (by destroying the pest organisms), competitors function by occupying and using resources in a nonpathogenic manner and in so doing exclude pathogenic organisms from colonizing plant tissues. Microbes which negatively affect pathogenic organisms are referred to as antagonists.