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Updated: April 17, 2002

Larvacides for mosquito control

The Environmental Protection Agency (EPA) evaluates and registers (licenses) pesticides to ensure that they can be used safely. These pesticides include products used in the mosquito control programs that states and communities have established. To evaluate any pesticide, EPA assesses a wide variety of tests to determine whether a pesticide has the potential to cause adverse effects on humans, wildlife, fish and plants, including endangered species and non-target organisms.
Officials responsible for mosquito control programs make decisions to use pesticides based on an evaluation of the risks to the general public from diseases transmitted by mosquitoes or on an evaluation of the nuisance level that communities can tolerate from a mosquito infestation. Based on surveillance and monitoring, mosquito control officials select specific pesticides and other control measures that best suit local conditions in order to achieve effective control of mosquitoes with the least impact on human health and the environment. It is especially important to conduct effective mosquito prevention programs by eliminating breeding habitats or applying pesticides to control the early life stages of the mosquito. Prevention programs, such as elimination of any standing water that could serve as a breeding site, help reduce the adult mosquito population and the need to apply other pesticides for adult mosquito control. Since no pesticide can be considered 100 percent safe, pesticide applicators and the general public should always exercise care and follow specified safety precautions during use to reduce risks. This fact sheet provides basic information on larvicides, a type of pesticide used in mosquito control programs.

The mosquito goes through four distinct stages during its life cycle:

egg - hatches when exposed to water;
larva - (plural. - larvae) lives in the water; molts several times; most species surface to breathe air;
pupa - (plural - pupae) does not feed; stage just prior to emerging as adult;
adult - flies short time after emerging and after its body parts have hardened.

What are Larvicides?

Larvicides kill mosquito larvae. Larvicides include biological insecticides, such as the microbial larvicides Bacillus sphaericus and Bacillus thuringiensis israelensis. Larvicides include other pesticides, such as temephos, methoprene, oils, and monomolecular films. Larvicide treatment of breeding habitats help reduce the adult mosquito population in nearby areas.

How are Larvicides Used in Mosquito Control?
State and local agencies in charge of mosquito control typically employ a variety of techniques in an Integrated Pest Management (IPM) program. An IPM approach includes surveillance, source reduction, larviciding and adulticiding to control mosquito populations. Since mosquitoes must have water to breed, source reduction can be as simple as turning over trapped water in a container to undertaking large-scale engineering and management of marsh water levels. Larviciding involves applying pesticides to breeding habitats to kill mosquito larvae. Larviciding can reduce overall pesticide usage in a control program. Killing mosquito larvae before they emerge as adults can reduce or eliminate the need for ground or aerial application of pesticides to kill adult mosquitoes.

More information:

For more information about mosquito control in your area, contact your state or local health department. Other resources for information on public health, disease control, and mosquito control include the following:

Centers for Disease Control and Prevention (CDC)
Tel: 970-221-6400
Fax: 970-221-6476
E-mail: dvbid@cdc.gov
Web site: cdc.gov

National Pesticide Information Center (NPIC)
Tel: 1-800-858-7378
E-mail: npic@ace.orst.edu
Web site: http://npic.orst.edu/

West Nile Virus Resource Guide: http://npic.orst.edu/wnv/
American Mosquito Control Association (AMCA)
Joseph M. Conlon, Technical Advisor
Tel/Fax: (904) 215-3008
E-mail: amca@earthlink.com