Biological Control Agents: Predators

Arthropod predators include a large number of insect species, as well as spiders and predatory mites. Predatory insects are found in approximately 20 insect orders. Insect predators are distinquished from insect parasitoids by a series of characteristics including: (1) killing and consuming more than one prey item to complete development, (2) relatively large size compared to prey, (3) typically being predaceous as both immatures and adults, (4) immatures are free living and active, with well developed sensory and locomotory organs, and (5) prey are consumed immediately, except with predatory wasps that store prey for immatures.

Because of their larger size, predators are more easily recognized than parasitoids. However, due to the nature of predation, our understanding of prey specificity is much poorer than that for insect parasitoids. The dietary habits of predators range from monophagous (very specific), feeding on one prey species, to oligophagous (narrow range), feeding on few closely related species, to polyphagous (general feeders) that consume a wide range of prey, fungi, and plant materials (e.g. nectar and pollen). For certain species, symbiotic microorganisms supply nutrients for development and reproduction.

A knowledge of predator and prey phylogeny is important to understand prey specificity and prey preference. Female oviposition behavior plays a role in determining the prey that are available to predaceous larvae. The type of prey consumed by a predator results from the interaction of several factors including the relative abundance of prey, predator foraging behaviors, and the nutritional suitability of prey.

Some of the best examples of importation biological control involve the use of highly prey specific predators including the coccinellid beetles, Rodolia (Vedalia) cardinalis and Cryptognatha nodiceps. Selected predatory species, including specialists and generalists, are mass reared and sold commercially for augmentative biological control, for example, phytoseiid mites, and both chrysopid (Neuroptera) and coccinellid species.