Classical and Augmentative Biological Control

Abstract

Parasitoids, predators, herbivorous arthropods, and plant pathogens may fail to follow an invasive species to new regions, allowing great increases in the invading species’ density. Introduction of the missing natural enemies, once their safey has been demonstrated to the local fauna or flora, is termed classical biological control. Classical biological control is a major tool in reducing impacts of invasive species, both in crops and natural areas, and has successfully control several hundred invasive species, completely and permanently in invaded countries. This form of restoration ecology is a basic tool in invasive species management and should be considered whenever the objective is to permanently reduce the density of an invasive species over a large area. In contrast, augmentative biological control seeks only to protect a crop during its period of production and permanent pest suppression is not intended or possible. Natural enemies used in augmentative biological control are reared in insectaries, often by commercial firms. This approach is used against insects and mites, but not weeds. The value of this approach depends on efficacy and cost of the natural enemy and augmentative biological control is most effective in greenhouse crops. Classical biological control is less polluting than use of pesticides and is often the only practical approach to suppression of invasive weeds or insects in wild lands. Both classical and augmentative biological control are harmless to people and vertebrates. Risks to nontarget plants or native insects may exist, depending on the host specificity of the agents use, and such risks can be managed to low levels by careful screening of the species employed.