page_title: Biological pest control
section_title: Importation
hierarchical_section_title: Biological pest control / Types of biological pest control / Importation
caption_attribution_description: Alternanthera philoxeroidesDeutsch: Alligatorkraut English: Alligator weed
context_page_description: Biological control or biocontrol 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 programs.
  There are three basic strategies for biological pest control: classical, where a natural enemy of a pest is introduced in the hope of achieving control; inductive, in which a large population of natural enemies are administered for quick pest control; and inoculative, in which measures are taken to maintain natural enemies through regular reestablishment.
  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.
context_section_description: Importation or classical biological control involves the introduction of a pest's natural enemies to a new locale where they do not occur naturally. Early instances were often unofficial and not based on research, and some introduced species became serious pests themselves.
  To be most effective at controlling a pest, a biological control agent requires a colonizing ability which allows it to keep pace with changes to the habitat in space and time. Control is greatest if the agent has temporal persistence, so that it can maintain its population even in the temporary absence of the target species, and if it is an opportunistic forager, enabling it to rapidly exploit a pest population.
  One of the earliest successes was in controlling Icerya purchasi (cottony cushion scale) in Australia, using a predatory insect Rodolia cardinalis (the vedalia beetle). This success was repeated in California using the beetle and a parasitoidal fly, Cryptochaetum iceryae. Other successful cases include the control of Antonina graminis in Texas by Neodusmetia sangwani in the 1960s.
  Damage from Hypera postica, the alfalfa weevil, a serious introduced pest of forage, was substantially reduced by the introduction of natural enemies. 20 years after their introduction the population of weevils in the alfalfa area treated for alfalfa weevil in the Northeastern United States remained 75 percent down.
  Alligator weed was introduced to the United States from South America. It takes root in shallow water, interfering with navigation, irrigation, and flood control. The alligator weed flea beetle and two other biological controls were released in Florida, greatly reducing the amount of land covered by the plant. Another aquatic weed, the giant salvinia (Salvinia molesta) is a serious pest, covering waterways, reducing water flow and harming native species. Control with the salvinia weevil (Cyrtobagous salviniae) and the salvinia stem-borer moth (Samea multiplicalis) is effective in warm climates, and in Zimbabwe, a 99% control of the weed was obtained over a two-year period.
  Small commercially reared parasitoidal wasps, Trichogramma ostriniae, provide limited and erratic control of the European corn borer (Ostrinia nubilalis), a serious pest. Careful formulations of the bacterium Bacillus thuringiensis are more effective.
  The population of Levuana iridescens, the Levuana moth, a serious coconut pest in Fiji, was brought under control by a classical biological control program in the 1920s.
caption: The invasive species Alternanthera philoxeroides (alligator weed) was controlled in Florida (U.S.) by introducing alligator weed flea beetle.
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