Permethrin, Resmethrin, Sumithrin: Synthetic Pyrethroids For Mosquito Control

Questions on Pesticides?

National Pesticide Information Center (NPIC)
1-800-858-7378

Current as of: April 17, 2002

Mosquito Life Cycle / Synthetic Pyrethroids / Resources

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.

What is the Mosquito Life Cycle?

Leon County Mosquito Control, Tallahassee, FL

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 Synthetic Pyrethroids?

Pyrethroids are synthetic chemical insecticides that act in a similar manner to pyrethrins, which are derived from chrysanthemum flowers. Pyrethroids are widely used for controlling various insects. Permethrin, resmethrin, and sumithrin are synthetic pyrethroids commonly used in mosquito control programs to kill adult mosquitoes.

Permethrin has been registered by EPA since 1977. It is currently registered and sold in a number of products such as household insect foggers and sprays, tick and flea sprays for yards, flea dips and sprays for cats and dogs, termite treatments, agricultural and livestock products, and mosquito abatement products.
Resmethrin has been registered by EPA since 1971 and is used to control flying and crawling insects in the home, lawn, garden, and industrial sites. It can also be used to control insects on ornamental plants (outdoor and greenhouse use), on pets and horses, and as a mosquitocide. Because of its toxicity to fish, resmethrin is a Restricted Use Pesticide (RUP) that is available for use only by certified pesticide applicators or persons under their direct supervision.
Sumithrin has been registered by EPA since 1975 and is used to control adult mosquitoes and as an insecticide in transport vehicles such as aircraft, ships, railroad cars, and truck trailers. It is also used as an insecticide and miticide in commercial, industrial, and institutional nonfood areas, in homes and gardens, in greenhouses, and in pet quarters and on pets.

How are Synthetic Pyrethroids Used in Adult Mosquito Control?

Most pyrethroid mosquito control products can be applied only by public health officials and trained personnel of mosquito control districts. Mosquito control professionals apply pyrethroids as an ultra low volume (ULV) spray. ULV sprayers dispense very fine aerosol droplets that stay aloft and kill adult mosquitoes on contact. Pyrethroids used in mosquito control are typically mixed with a synergist compound, such as piperonyl butoxide, which enhances the effectiveness of the active ingredient. The product is often diluted in water or oil and applied at rates less than 1/100th of a pound of active ingredient or less than 4 fluid ounces of mixed formulation per acre.

Do Pyrethroids Pose Risks to Human Health?

Pyrethroids can be used for public health mosquito control programs without posing unreasonable risks to human health when applied according to the label. Pyrethroids are considered to pose slight risks of acute toxicity to humans, but at high doses, pyrethroids can affect the nervous system.

Do Pyrethroids Pose Risks to Wildlife or the Environment?

Pyrethroids used in mosquito control programs do not pose unreasonable risks to wildlife or the environment. Pyrethroids, when applied at mosquito control rates, are low in toxicity to mammals, and are practically nontoxic to birds. Mosquito control formulations of permethrin break down in the environment, and high temperatures and sunlight accelerate this process. However, pyrethroids are toxic to fish and to bees. For that reason, EPA has established specific precautions on the label to reduce such risks, including restrictions that prohibit the direct application of products to open water or within 100 feet of lakes, streams, rivers or bays.

What is The Current Regulatory Status of Pyrethroids?

As part of its responsibility to reassess all pesticides registered before 1984, EPA has given highest priority to reviewing more acutely toxic pesticides such as organophosphates and carbamates. Organophosphates are currently under review. Comprehensive reviews of the synthetic pyrethroids are scheduled for approximately 2004.

Where Can I Get More Information About Synthetic Pyrethroids and Mosquito Control?

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: http://www.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

For more information regarding public health mosquito control or strategies for controlling mosquitoes around your home, contact EPA headquarters or one of the 10 regional offices.

Other Helpful EPA Publications

Mosquitoes: How to Control Them (735-F-02-005)
Malathion for Mosquito Control (735-F-02-006)
Larvicides for Mosquito Control (735-F-02-007)
Naled for Mosquito Control (735-F-02-008)
Synthetic Pyrethroids for Mosquito Control (735-F-02-009)

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