Interactions Between Fungal Pathogens and Insect Hosts

Fungal diseases in insects are common and widespread and often decimate insect populations in spectacular epizootics. Virtually all insect orders are susceptible to fungal diseases. Fungi infect insects by breaching the host cuticle; they are the principal pathogens among sucking insects because these hosts cannot ingest other pathogens that infect through the gut wall. Fungi are also particularly important for control of Coleoptera, because viral and bacterial diseases are rare among beetles. Entomopathogenic fungi are associated with insects living in diverse habitats, including fresh water, soil, soil surfaces, and aerial locations. Currently, widely publicized environmental concerns and health risks associated with use of synthetic chemical insecticides have stimulated efforts to develop biological-control agents as alternatives or supplements to these chemicals. Consequently, much recent interest in mycoinsecticides has led to the marketing of several of them. Nevertheless, of the 700 species of entomopathogenic fungi currently known, only 10 species have been, or are presently being, developed for control (85, 89, 101, 130, 136), and the full potential of entomopathogenic fungi has not been approached. To develop fungi for control purposes, we need to understand the requirements for the high levels of disease transmission in the field that are characteristic of epizootics. In-depth epizootiological studies of several systems have been undertaken, in some cases resulting in simulation models used for experi­ mentation with these complex systems as well as for development of control