Chapter 18 - A Perspective on Pathogens as Biological Control Agents for Insect Pests

Abstract

Pathogens that cause disease in insects fall into four main groups—viruses, bacteria, fungi, and protozoa. This chapter describes each of these groups in terms of the biological properties that determine their utility as agents for controlling insects. It provides a brief historical review and a preliminary description of strategies for using pathogens in control programs. One of the viruses used for such purpose are iridoviruses that are nonoccluded viruses with a linear double-stranded DNA genome that produce large icosahedral virions replicating in the cytoplasm of a wide range of tissues in infected hosts, causing disease that is generally fatal. Virions can form paracrystalline arrays in infected tissues, imparting an iridescent hue to the infected hosts. The bacteria are relatively simple unicellular microorganisms that lack internal organelles such as a nucleus and mitochondria and reproduce by binary fission. With a few exceptions, most of those used as microbial insecticides grow readily on a wide variety of inexpensive substrates, a characteristic that greatly facilitates their mass production. The majority of bacteria currently being used or under development as the microbial control agents for insects are spore-forming members of the bacterial family Bacillaceae and belong to the genus Bacillus. These insect-pathogenic bacilli occur in healthy and diseased insects, but also occur in, and can be isolated from, many other habitats including insect frass, soil, plants, granaries, and aquatic environments.