Biological control agent

Biological control is a method of controlling pests such as insects, mites, weeds and plant diseases using other organisms. It relies on predation, parasitism, herbivory, or other natural mechanisms, but typically also involves an active human management role. It can be an important component of integrated pest management (IPM) programs.

There are three basic types of biological pest control strategies: importation (sometimes called classical biological control), in which a natural enemy of a pest is introduced in the hope of achieving control; augmentation, in which locally-occurring natural enemies are bred and released to improve control; and conservation, in which measures are taken to increase natural enemies, such as by planting nectar-producing crop plants in the borders of rice fields.

Natural enemies of insect pests, also known as biological control agents, include predators, parasitoids, pathogens, and competitors. Biological control agents of plant diseases are most often referred to as antagonists. Biological control agents of weeds include seed predators, herbivores and plant pathogens.

Biological control can have side-effects on biodiversity through attacks on non-target species by any of the same mechanisms, especially when a species is introduced without thorough understanding of the possible consequences.

The term "biological control" was first used by Harry Scott Smith at the 1919 meeting of the Pacific Slope Branch of the American Association of Economic Entomologists, in Riverside, California. It was brought into more widespread use by the entomologist Paul H. DeBach (1914–1993) who worked on citrus crop pests throughout his life. However, the practice has previously been used for centuries. The first report of the use of an insect species to control an insect pest comes from "Nan Fang Cao Mu Zhuang" (南方草木狀 Plants of the Southern Regions) (ca. 304 AD), attributed to Western Jin dynasty botanist Ji Han (嵇含, 263–307), in which it is mentioned that "Jiaozhi people sell ants and their nests attached to twigs looking like thin cotton envelopes, the reddish-yellow ant being larger than normal. Without such ants, southern citrus fruits will be severely insect-damaged". The ants used are known as huang gan (huang = yellow, gan = citrus) ants (Oecophylla smaragdina). The practice was later reported by Ling Biao Lu Yi (late Tang Dynasty or Early Five Dynasties), in Ji Le Pian by Zhuang Jisu (Southern Song Dynasty), in the Book of Tree Planting by Yu Zhen Mu (Ming Dynasty), in the book Guangdong Xing Yu (17th century), Lingnan by Wu Zhen Fang (Qing Dynasty), in Nanyue Miscellanies by Li Diao Yuan, and others.

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