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Mosquito Control

The District uses many different means of controlling mosquitoes.
Biorational and chemical control 
May contain: outdoors, nature, land, water, grassland, field, plant, grass, human, and person

The District routinely applies "biorational" pesticides countywide to control mosquitoes. The term "biorational" relates to the application of naturally occurring mosquito pathogens and predators in a manner that provides effective mosquito control with the least amount of impact on the environment. Currently, the District uses several biorationals including two microorganisms, Bascillus thuringiensis israelensis (Bti) and Bascillus sphaericus plus an insect growth regulator, methoprene.

To learn more about what the District uses, please click here.

Biological Control


May contain: animal, fish, and carp

The District uses mosquito fish (Gambusia affinis) as biological control agents in water sources that can sustain immature mosquitoes. These fish are not native to California, so they are only used in water sources that do not connect or drain to natural water bodies. Sources that would fall under this category would be unused swimming pools and or spas, ornamental ponds, water troughs, etc.

 To learn more about mosquitofish and to download fish pick-up forms, please click here. 

Physical Control
May contain: plant, grass, outdoors, nature, land, and water

Physical control or manipulating the environment to reduce mosquito breeding sites is a very effective method of mosquito control. A few examples of physical control include: promoting effective drainage, controlling vegetation and reducing backyard breeding sources.

Source Reduction

Manipulating or eliminating potential mosquito breeding sources can provide a dramatic reduction in mosquito populations. District staff educate property owners as to ways in which they can remove these sources like by emptying containers holding water. Staff also works with large land managers to restore and maintain water flow or circulation in systems that become clogged with sediment and debris or over run with vegetation.

To learn the various ways you can eliminate breeding sources around your home, please click here.