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Controlling Mosquitoes at the Larval Stage

Larvicides may be applied to water in which larvae or pupae are developing. Pastures, irrigation ditches, dairy waste ponds, sloughs, catch basins, storm drains and roadside ditches are examples of areas the District regularly inspects to reduce mosquito populations.

Larvicides target larvae in the breeding habitat before they can mature into adult mosquitoes and disperse. Larvicide treatment of breeding habitats helps reduce the adult mosquito population in nearby areas.

Liquid larvicide products are applied directly to water using backpack and truck sprayers or aircraft-mounted sprayers. Tablet, pellet, granular, and briquet formulations of larvicides are also applied by mosquito control technicians to breeding areas.

While there are several registered active ingredients used in larvicides, below are some commonly used larvicides. EPA’s evaluation of mosquito control product includes assuring that it does not pose risks to vulnerable populations, including children and pregnant women when used according to label directions. 

Bacterial Insecticides

Insects that are exposed to the Bacillus species have trouble digesting food they eat after the exposure then they die.

  • Bacillus thuringiensis israelensis ( Bti ) for mosquito control        Bti information
  • Bacillus sphaericus

Insect Growth Regulators

Insect growth regulators prevent the larvae from maturing into adult mosquitoes.

  • Methoprene

Organophosphate Insecticides

The organophosphate insecticides affect the nervous system of insects.

This pesticide is applied to standing water, shallow ponds, lakes, woodland pools, tidal waters, marshes, swamps, catch basins, and other areas where mosquitoes can breed.

Other Materials

Oils and films disperse as a thin layer on the surface of the water and cause larvae and pupae to drown. 

  • Mineral Oils
  • Monomolecular Films