How Insect Pathogens are used for Insect Control

Insect pathogens are used in IPM in at least three different ways; inundative applications, inoculative releases, management of naturally occurring pathogens, and introduction of exotic pathogens as classical biological control agents. There is considerable overlap between these four arbitrary groups.

Inundative applications are those in which insect pathogens are applied in large quantities with the goal of killing as many individuals of the pest population as quickly as possible. Pathogens used in this manner are called microbial insecticides. Replication of the pathogen in the host and production of additional infectious propagules may be desirable, but is not usually not required for microbial insecticides to be effective..

Inoculative applications.

Inoculative applications are those in which small quantities of insect pathogens are applied or released into an insect host population. The goal of this type of release is to produce infections in at least a few hosts, which will, in turn, produce numerous infectious propagules that will infect many more susceptible hosts.

Introduction of exotic pathogens as classical biological control agents.

Hundreds of exotic parasitoids and predators have been introduced into the US as classical biological control agents since the vedalia beetle was brought into California for the control of the cottony cushion scale in 1889. In contrast, fewer than five exotic species of pathogens have been intentionally introduced as biological control agents. Difficulties in identifying and isolating insect pathogens, along with regulatory uncertainties, have contributed to the underutilization of insect pathogens as exotic biological control agents.

Management of naturally occurring pathogens.

Insect pathogens are important components of the natural enemy complex of many insect species, including pest species. Some groups of pathogens, such as microsporidia, may not always maintain host insect densities below economic thresholds, but they suppress the rapid increase of pest populations and are often responsible for the decline of populations that have exceeded the economic threshold. In most cases the major goal for managing naturally occurring insect pathogens is to elicit an epizootic earlier in the season, before the host densities have exceeded the economic threshold. This can be accomplished by inoculative releases of the pathogen or by changing cultural practices to promote an epizootic.

Types of Pathogens

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