Chemical Control

ChemicalsChemical control of mosquitoes is the application of natural or manmade compounds (insecticides) to reduce mosquito populations to tolerable levels. Chemical control methods are applied to obtain immediate control when physical and biological control methods fail to maintain mosquito numbers below a tolerable level or during an epidemic of mosquito-borne disease when emergency control measures are needed. The District is signatory to a National Pollution Discharge Elimination System (NPDES) permit for applications of larvicides in surface waters. The permit is granted by the State Water Quality Control Board, which reviews the District’s mosquito control activities in local waterways.

The District follows accepted principles of proper pesticide usage which includes:

  1. Using pesticides as a last resort to complement biological, physical or natural controls.
  2. Appling pesticides in a manner that minimizes harm to non-target organisms.
  3. Using pesticides to treat specific sites where mosquitoes (which are causing annoyance or creating a public health problem) are breeding.
  4. Applying pesticides selectively to the proper life stage of the mosquito.
  5. Applying pesticides in a manner that will minimize personal hazard to the applicator and other persons in the vicinity.
  6. Applying pesticides in accordance with federal and state laws and regulations, and in compliance with the label.

Treatmment WasteLarvicides may be applied to water in which larvae or pupae are developing. Pastures, septic tanks, irrigation ditches, animal waste ponds, creeks, sloughs, catch basins, and roadside ditches are examples of areas the District regularly inspects to reduce mosquito populations.

Adulticides may be applied as space sprays, mists, or fogs to kill adult mosquitoes and as a residual insecticide on surfaces likely to be contacted by adult mosquitoes. Adulticides are applied by hand held equipment as well as, truck mount, and aerial mounted equipment.

List of Materials Used

West Nile Virus and
Dead Bird Hotline

(877) 968-BIRD (2473)

or online at

Stay Informed!
Get Email Updates.

Sign up to receive email updates including news releases and spray updates.