Biological control is usually defined as the use of natural enemies to suppress populations of pests such as insects and weeds. In new areas or countries, pests often arrive without the suite of natural enemies which would normally keep then in check in their natural range. Consequently they sometimes undergo periods of outbreak before existing predators, parasitoids or diseases adapt to them, and before pest management strategies, including biological control can be developed.
Biological control has a long history dating back to 200 A.D. when the Chinese used natural enemies to control insect pests. Ants were used (and nests of ants sold) to control citrus insect pests, and ants were also used in 1200 A.D. in Yemen for control of date palm pests by moving nests from the wild and placing them in the trees. At about the same time ladybird beetles were recognised as being useful for control of aphids and scale insects. For more on the history of biological control see Simmonds et al. (1976). In New Zealand the earliest biological control agent introduction was Coccinella undecimpunctata, a coccinellid predator released in 1874 to attack aphids (Cameron et al. 1993).
Biological control can be used for pest management in a number of ways:
- Classical biological control: natural enemies from the country of origin of the pest are identified, and one or more are imported and released to control the pest. It is expected that the biological control agent will establish permanently from the relatively small founder populations released, and that they will reproduce and spread. For general texts see Caltagirone (1981) and Bellows and Fisher (1999).
- Augmentative biological control: this is often used in cases where the natural enemy is unable to establish and survive in the environment where its host has become a pest. Augmentative biological control can be inundative, when the natural enemies are released in high numbers to achieve control over a short period (e.g. for glasshouse crop pests), or inoculative, when fewer biological control agents are released which are able to build up in numbers during favourable seasons, but fail to overwinter. For general text see van Lenteren (2000).
- Conservation biological control: this strategy is focused on enhancing natural biological control. For example, crops can be sown with strips or borders of plants which are beneficial to existing natural enemies serving as a refuge or source of food so that they can increase their abundance. For general texts see Barbosa (1998) and van Emden (2003).
Barbosa P. (1998). Conservation biological control. Academic Press, London.
Bellows T.S. and Fisher T.W. (1999). Handbook of Biological Control: Principles and Applications of Biological Control. Academic Press, San Diego.
Caltagirone L.E. (1981). Landmark examples in classical biological control. Annual Review of Entomology 26: 213-232.
Cameron P., Hill R.L., Bain J., Thomas W.P. (1993). Analysis of importations for biological control of insect pests and weeds in New Zealand. Biocontrol Science and Technology 3: 387-404.
Simmonds F.J., Franz J.M. and Sailer R.I. (1976). History of biological control. Pp. 788 In: Practice of biological control, C.B. Huffaker and P.S. Messenger (Ed.) Academic Press, New York.
van Emden H.F. (2003). Conservation biological control: from theory to practice. In: Proceedings of the 1st International Symposium on Biological Control of Arthropods, R. Van Driesche (Ed.) United States Department of Agriculture Forest Service, Washington, USA.
van Lenteren J.C. (2000). Success in biological control of arthropods by augmentation of natural enemies. Pp. 77-103 In: Measures of Success in Biological Control, G. Gurr and S. D. Wratten (Ed.) Kluwer Academic Publishers, Dordrecht