Biocontrol, or biological control, is the natural or applied regulation of populations of pest organisms—especially insects—through the role or use of natural enemies. In other words, biocontrol uses living organisms to reduce and eliminate pest abundance and damage. The agents through which biocontrol is accomplished are varied. For example, biocontrol agents can be consumers of pests; thus, herbivores are used to reduce weeds, whereas predators or parasites are employed to diminish the number of insect and other animal pests. In addition, pathogens and competitors that interact with pests are often utilized in biocontrol. Typically, agricultural and forest pests are the major targets of biocontrol. Notably, biocontrol operates as an alternative to the use of pesticides that may be harmful to the environment. See also: Agricultural science (animal); Agricultural science (plant); Agricultural soil and crop practices; Agriculture; Biological insect control; Forest; Forestry; Insecta; Parasitology; Pathogen; Predator-prey interactions; Weeds
One of the most important biocontrol methods involves the importation of a nonindigenous species that is used as a biocontrol agent to suppress a nonindigenous invasive pest. Also termed "classical biocontrol" or "importation biocontrol," this method is used when the damaging pest species is not indigenous to the region or area in which it is problematic. The damaging effects of the invasive pest, though, can be minimized by importing another species that is known to consume the pest in its native (indigenous) range. In the past, researchers have attempted, with varying degrees of success, to lessen the effects of moths, aphids, beetles, thrips, scales, and other insect pests that damage crops. However, for the successful practice of this type of biocontrol, accurate knowledge of the ecology of the pest and the biocontrol agent is necessary. Moreover, scientists must be able to identify the target pests and any potential biocontrol agents, locate regions (often in foreign countries) that contain these biocontrol agents, quarantine and rear these agents in facilities far from their natural habitat, and predict the success of the imported agents as well as the effects on nontarget species. See also: Economic entomology; Ichneumon wasps as biological control agents; Invasion ecology
Environmentally, the use of importation biocontrol provides a natural substitute for the use of toxic pesticides and insecticides. It also offers a control option in cases where pests have developed resistance to chemical control compounds. In addition, importation biocontrol agents are self-sustaining; that is, once an importation agent is established, few or even no further measures are required for future control. Still, the deliberate introduction of any nonindigenous species to a nonnative location can lead to unintended environmental consequences. Therefore, an imported biocontrol agent must be evaluated carefully to determine if it would attack and harm other nonpest species. See also: Insecticide; Pesticide