All Issues

The mosquito control program in California has been uniquely successful, and for practical purposes, the major mosquito-borne diseases, such as encephalitis and malaria, have been effectively controlled in the state in recent years. Much of the original research leading to this success was done by the University of California School of Public Health. Current research is directed at preventing a resurgence of mosquito-borne diseases, with emphasis on surveillance and vector suppression.

Research on mosquito biology and ecology yields fundamental knowledge of the behavior, habits, breeding preferences, flight range, survival rates, and other characteristics of pest and disease-vector mosquitoes-information essential for effective planning and execution of control programs. Ecological studies assume greater importance in California than elsewhere because of the state's diverse climate and topography. Forty-nine mosquito species are found here, of which six are confirmed disease vectors.

Control of mosquitoes through exploitation of their natural enemies to suppress them has been given high priority in California for many years. More studies have been approved and more funds expended on biological controls than on any other research category. Investigations have been pursued on a broad range of bioagents—mosquito predator fish, aquatic insects, fungal and bacterial pathogens, and nematode parasites.

Although they have fallen into disfavor because of mosquito resistance and other problems, chemicals are still the fastest and most effective way to suppress mosquitoes. The thrust of nearly all University research in this area is on the development and evaluation of narrow spectrum insecticides that selectively kill mosquitoes with minimal injury to natural enemies and nontarget species. Promising new developments include insect growth regulators, which interfere with the growth processes of the mosquito larvae, juvenile hormones, mosquito attractants, repellents, and other substances derived from natural products.

Physical control involves modification of the environment to reduce or eliminate mosquito breeding places: drainage, diking, filling, leveling, or other engineering works. Cultural control aims for mosquito reduction through management of soils and vegetation that contribute to mosquito problems. Researchers are investigating the effects of conventional drainage and ditching practices on natural flow and fauna in salt marshes and studying ways to reclaim impermeable alkali soils, which are important sources of mosquitoes in some areas.