Biological pest controls use the natural enemies of pests to kill or reduce their impact. Biological controls require introducing predator or parasite species to kill the pest. Humans introduce the biological controls into areas where the pest is a problem, though these controls often exist naturally in other areas. Though biological controls may not completely eradicate a pest, using biological controls offer advantages over other control methods such as pesticides.
Biological pest control creates no chemical run-off in waterways or soil pollution. The people using biological controls don't have to worry about the health effects of handling lady beetles, lace wings and other biological control agents, as opposed to the health risks of working with pesticides. Organic farmers can use biological controls without fear of losing their organic certification.
Biological pest control targets a narrow range of pests, sometimes even a single species. Other, beneficial insects, birds, reptiles and animals living in the area remain unharmed. Pesticides may kill everything in their path, and effect species outside the targeted pest, such as happened when DDT used to kill mosquitoes and other pests threatened to wipe out birds such as the peregrine falcon.
David Kazmer and Michael Brewer of Montana State University report that biological pest controls produce as much as $32 of benefit for every $1 invested, while chemical controls average only $2.50 in benefits for each $1 invested.
Successfully established biological control species will maintain stable populations for generations without need for additional investment by humans. Chemical controls, however, must be applied each season, sometimes multiple times a season. This adds to both the environmental and monetary costs of using chemical pest controls.