Published by Australian Academy of Science
A plague on the pest – rabbit calicivirus disease and biological control Box 1 | Biological control

Biological control is the use of one living organism to control another. For example, the moth Cactoblastis cactorum was imported to Australia from South America to control prickly pear. This resulted in about 250,000 square kilometres of agricultural land being cleared of prickly pear.

In their natural environment, most organisms are kept under control by their natural enemies (parasites, predators and diseases that have evolved with them over a long period of time). But when an animal or plant is transferred, either accidentally or deliberately, to a new environment, its natural enemies are often left behind. Free of restraint, it may increase out of control and become a pest. Australia has been particularly vulnerable in the last 200 years because immigrants did not see any value in Australian flora and fauna and so imported plants and animals for food, ornamental purposes, hunting or just to make Australia look more like their homelands. Most Australian insect pests and weeds have been introduced from other countries, where they are controlled by naturally occurring predators or parasites.

In a typical program of biological control in Australia, scientists attempt to find a pest's natural enemies in its original habitat. If a promising predator or disease is found, it is tested to ensure that it does not attack other species. If after these tests it is considered safe, it is released as a biological control organism.

When successful, biological control has important advantages over other methods. It is specific to the pest, and so does not affect other organisms or the environment. It is self-perpetuating and involves minimal cost after the initial research.

Related sites

• Control of introduced species (Questacon, Australia)

• Classical biological control (CSIRO, Australia)

• Biocontrol (University of Adelaide, Australia)

• Killer water weed (Australia advances, CSIRO)

Other boxes

Box 2. The history of myxoma virus in Australia

Box 3. Estimating population size and density