Biological control for insects is a procedure that seeks to control pest insects in a more natural way. Some of the different biological controls for insects include classical biological control, conservation methods, and augmentation. Classical biological control includes introducing a pest's enemies into an area in order to control the pest. The conservation method deals with conserving the natural enemies of the pest. Lastly, augmentation seeks to change the environment to allow for better control over an undesirable insect.
When an exotic species of insect is introduced into an area, without its natural predators and pathogens, that insect could breed and multiply until it becomes a pest. In such cases, classical biological control can be used to counteract the exotic species. This type of biological control for insects uses the exotic insect's native enemy to control the pest population. The cultivation and release of these pest enemies is carefully researched and implemented.
Pest enemies can take the form of predators, parasitoids, and pathogens. A parasitoid is an animal that kills another by using it as a host during a stage in its development. When introducing a pest enemy into an area where a pest has been established, it is first necessary to determine the species of the pest and choose a suitable enemy. Once chosen, the enemy is released so it can establish itself after it has been quarantined to ensure no undesirable parasitoid or pathogen is present. The timing of the pest's enemies' release should also coincide with the appropriate stage in the pest's life cycle.
Sometimes, native insect species can become pests when the populations of their natural enemies are reduced, often because of pesticides. In cases like these, conservation is a method of biological control for insects that attempts to conserve the pest species' natural enemies. Many times, this method employs the reduction of pesticides that could be decimating the pest's natural enemies, or a switch to pesticides that have a lesser effect on the predators in question. In addition, conservation includes growing certain plants that support the pest's enemies.
Another method of biological control for insects — augmentation — involves controlling the pest population by seasonally introducing the pest's natural enemies. Unlike the classical method of biological control, the idea here is not to establish the pests’ predators permanently in the environment but simply release them annually to control the season’s pests. There are two methods for releasing insects under the augmentation method of biological control for insects: inoculative and inundative. With an inoculative release, a person releases a small amount of the pest's predators at a certain time in the growing season. These predators then breed and multiply on their own. In contrast, the inundative approach involves releasing a large number of these enemy species at once. In either case, the predators die off naturally after the season.