The classical biological control means the introduction of natural enemies to a new location where they do not occur naturally. They originate from other place and introduced to new locales. It is usually done by the government authorities. In many examples, the complex of natural enemies related with an insect pest is not sufficient. It is especially evident when there is an accidental introduction of an insect pest into a new geographic area in absence of its associated natural enemies. These introduced pests are called as exotic pests.
Scientists refer to the classical biological control for obtaining the required natural enemies. It includes the practice of importing, and releasing natural enemies for establishment so as to control an introduced (exotic) pest. This is practiced against native insect pests also. The first step in the process is the determination of the origin of the introduced pest followed by collection of proper natural enemies that are linked to the pest or closely related species. Then, a natural enemy is passed through a meticulous quarantine process for ensuring no unwanted organisms got introduced. They are produced on mass scale and released. It is followed by various follow-up studies to ensure the successful establishment of natural enemy at the site of release, and to measure its long-term benefits
There have been numerous successful examples of classical biological control programs. In 1800, the cottony cushion scale known as Icerya purchase, was controlled by using classical biological control programs. A predatory insect Rodolia cardinalis (the Vedalia Beetle) and a parasitoid fly were introduced by Charles Valentine Riley from Australia. The cottony cushion scale was completely controlled within a few years by these introduced natural enemies. The classical biological control is inexpensive and long lasting. Once, a natural enemy is established successfully, it rarely needs an additional input and continues to kill the pest without any human help.
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