Classical Biological Control

Importing natural enemies from abroad is an important step in pest management in part because many pest insects in the United States and elsewhere were originally introduced from other countries.
Accidental introductions of foreign pests have occurred throughout the world as a result of centuries of immigration and trade. Although the foreign origins of a few recently introduced pests such as the Asian tiger mosquito, Russian wheat aphid, and Mediterranean fruit fly are often noted in news stories, many insects long considered to be serious pests in this country are also foreign in origin. Examples of such pests include the gypsy moth, European corn borer, Japanese beetle, several scale insects and aphids, horn fly, face fly, and many stored-product beetles. In their native habitats some of these pests cause little damage because their natural enemies keep them in check. In their new habitats, however, the same set of natural enemies does not exist, and the pests pose more serious problems. Importing and establishing their native natural enemies can help to suppress populations of these pests.

Importation typically begins with the exploration of a pest's native habitat and the collection of one or several species of its natural enemies. These foreign beneficials are held in quarantine and tested to ensure that they themselves will not become pests. They are then reared in laboratory facilities and released in the pest's habitat until one or more species become established. Successfully established beneficials may moderate pest populations permanently and at no additional cost if they are not eliminated by pesticides or by disruption of essential habitats.

Importation of natural enemies has produced many successes. An early success was the introduction of the Vedalia beetle, Rodolia cardinalis, into California in 1889 for the control of cottony cushion scale on citrus. For over 100 years this predaceous lady beetle from Australia has remained an important natural enemy in California citrus groves.

Although the importation of new natural enemies is important to farmers, gardeners, and others who practice pest management, the scope of successful introduction projects (involving considerable expertise, foreign exploration, quarantine, mass rearing, and persistence through many failures) is so great that only government agencies commonly conduct such efforts. Introducing foreign species is not a project for the commercial farmer or home gardener.