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Pesticides: Mosquito Control

Who approves the use of pesticides?

The United States Environmental Protection Agency (USEPA) approves the use of pesticides nationally. Before pesticides are registered by USEPA, they must undergo laboratory testing for acute and chronic health effects. In these tests, laboratory animals are purposely fed a pesticide at high doses for an extended period of time specially to see if toxic effects occur. These tests help scientists judge how these chemicals might affect humans, domestic animals, and wildlife in the case of exposure.

Larval Control

Control of larval mosquitoes is the backbone of most mosquito control programs. Pesticides added to the water to kill mosquito larvae are called larvicides. These products may be applied by hand, with a power backpack, from all terrain vehicles (ATV’s) or trucks, and in very large or inaccessible areas with helicopters and airplanes. Pesticides used for larviciding (granular or liquid formulations) include, chemicals (organophosphates), bacterial products (Bacillus thuringiensis var. israelensis (Bti) and Bacillus sphaericus (Bs)); surface agents (monomolecular films that spread across the surface of the water); and the insect growth regulators methoprene and dimilin (chemicals that are added to the water to disrupt the normal maturation process of mosquito larvae).

Adult mosquito control

Adult mosquito control is a means to rapidly knockdown biting adult mosquitoes. This can become necessary when larval control measures are insufficient or not feasible. Pesticides used to kill adult mosquitoes are called adulticides. Adulticiding may be initiated when there is evidence of significant disease transmission in a region (WNV, WEE). The most common method of adult mosquito control (adulticiding) is ultra-low volume (ULV) spraying. ULV spraying is the process of putting very small amounts of liquid into the air as a fine mist of droplets. These droplets float on the air currents and quickly kill mosquitoes that come into contact with them. ULV adulticides are applied when mosquitoes are most active—typically early evening or pre-dawn.

ULV spraying is usually done over geographic areas consisting of several acres to many square miles. Unlike agricultural or structural pesticide applications where the chemical is applied directly to a crop or structure, a ULV formulation is sprayed into the air column where it can contact and kill active mosquitoes. Aerial movement of the ULV product is an essential part of the application. ULV applications are only done during environmental conditions that ensure desirable product movement.