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1. What are "larvicides" and "adulticides"?

Larvicides are products used to kill immature mosquitoes before they become adults. They can be either biological (such as toxin from specific bacteria that is lethal to mosquito larvae but not to other organisms) or chemical products, such as insect growth regulators, surface films, or organophosphates. Larvicides are applied directly to water sources that hold mosquito eggs or larvae. When used well, larvicides can help to reduce the overall mosquito burden by limiting the number of new mosquitoes that are produced. 

An example of a larvicide is Bacillus thuringiensis israelensis (BTI), which comes in products known as mosquito “dunks” or “donuts.” Adulticides are products used to kill adult mosquitoes. Adulticides can be applied from hand-held sprayers, truck-mounted sprayers, or using airplanes. Adulticides, when used well, can have an immediate impact to reduce the number of adult mosquitoes in an area, with the goal of reducing the number of mosquitoes that can bite people and possibly transmit the West Nile Virus. Both larvicides and adulticides are regulated by the U.S. Environmental Protection Agency.

2. What is CDC's position regarding the use of chemical mosquito control?

Chemical control measures are one part of a comprehensive and integrated mosquito management program. An integrated program is the most effective way to prevent and control mosquito-borne diseases. An integrated mosquito management program should include several components: 

• The ability to use chemical and biological methods to control both mosquito larvae and adult mosquitoes
• Community outreach and public education
• Reduction of mosquito breeding sites
• Surveillance (monitoring levels of mosquito activity, and where virus transmission is occurring)

Control measures, including the decision to use chemical adulticides (pesticides to kill adult mosquitoes), should be based on surveillance data and the risk of human disease.

3. How are mosquitoes controlled during outbreaks?

Adult mosquito control may be undertaken to combat an outbreak of mosquito-borne disease or a very heavy nuisance infestation of mosquitoes in a community. Pesticides registered for this use are known as adulticides and are applied either by aircraft or on the ground employing truck-mounted sprayers. State and local municipalities commonly use the organophosphate insecticides malathion and naled and the synthetic pyrethroid insecticides permethrin, resmethrin, and sumithrin for adult mosquito control. Check with your municipality to determine the exact adulticides used, if any. 

Mosquito adulticides are applied as ultra-low volume (ULV) sprays. ULV sprayers dispense very fine aerosol droplets that stay aloft and kill flying mosquitoes on contact. ULV applications involve small quantities of pesticide active ingredient in relation to the size of the area treated, typically less than 3 ounces per acre, which minimizes exposure and risks to people and the environment. Adulticides can be used for public health mosquito control programs without posing unreasonable risks to the general population or to the environment when applied according to the pesticide label. More information on pesticides commonly-used in public health mosquito control programs is available at the Environmental Protection Agency’s Pesticides website.

4. Are pesticides harmful to people?

Effect on human health is one of the primary factors considered in the regulation of pesticides. Pesticides that can be used for mosquito control have been judged by the Environmental Protection Agency not to pose an unreasonable risk to human health. People who are concerned about exposure to a pesticide, such as those with chemical sensitivity or breathing conditions such as asthma can reduce their potential for exposure by staying indoors during the application period (typically nighttime). 

A published study, (MMWR, July 11, 2003) examined illnesses in nine states associated with exposure to pesticides used to control mosquito populations from 1999 through 2002. This study found that and "application of certain insecticides poses a low risk for acute, temporary health effects among persons in areas that were sprayed and among workers handling and applying insecticides." This article can be viewed online. For more information on pesticides and health, consult the U.S. Environmental Protection Agency, which oversees the registration of these chemicals. The National Pesticide Information Center (NPIC) can also provide information through a toll-free number, 800-858-7378 or online.

5. What should I do if I think that I am having health problems because of pesticides used in my area?

If you are experiencing health problems for any reason it is important to see your health care provider promptly. If you are experiencing severe health problems go immediately to an Emergency Room.

6. How does pesticide spraying affect the environment?

A great deal of research must be done before pesticides can be used in the environment. The best source for finding out about the pesticides used in your area, and their effect on specific types of wildlife, is with the U.S. Environmental Protection Agency, which oversees the registration of these products. The National Pesticide Information Center (NPIC) can also provide information through a toll-free number, 800-858-7378 or online.

7. What training is required for workers who apply pesticides?

Each state has mandated training and experience requirements that must be met before an individual can commercially apply pesticides. In addition, these applicators must follow the instructions and precautions that are printed on the pesticide label. All pesticide products are required to have a label that provides information, including instructions on how to apply the pesticide and precautions to be taken to prevent health and environmental effects. All labels are required to be approved by the U.S. Environmental Protection Agency.

8. Where can I get information regarding the safety of specific pesticides?

Questions concerning specific pesticides can be directed to the U.S. Environmental Protection Agency, as this agency has responsibility for the registration of pesticides. Many issues are addressed on the Environmental Protection Agency’s Mosquito Control website. The National Pesticide Information Center (NPIC) provides pesticide information and questions about the impact of pesticide use on human health. NPIC is cooperatively sponsored by Oregon State University and the U.S. Environmental Protection Agency. NPIC can be reached online or toll-free at 800-858-7378.

9. How can I find out what types of pesticides are being used in my area?

Your city or town may or may not be using larvicides and adulticides for mosquito control. Check with your municipality to be sure. Another resource to learn more about mosquito control is the American Mosquito Control Association.