Ultra-low volume (ULV) adult mosquito treatments by helicopter are applied in areas with strong virus activity that has been detected multiple times.

The District’s Mosquito-Borne Virus Surveillance and Emergency Response Plan helps target control applications where risk of WNV transmission is greatest. Despite control efforts, surveillance in some areas may indicate unidentified sources of standing water maintaining ideal breeding conditions for mosquitoes.

Larval mosquito control targets immature mosquitoes in the water using a naturally occurring bacterium to kill mosquito larvae before they can develop into biting adults. The product is environmentally friendly, approved for application on organic crops, and has no effect on people or pets at the amounts used for mosquito control. It is registered with the U.S. Environmental Protection Agency and the California Department of Pesticide Regulation.

Adult control is only a small part of our overall program but a critical component to reduce disease transmission and protect the public from mosquito-borne disease. Ultra-low volume (ULV) treatments are carried out when the adult population of mosquitoes or infected mosquitoes passes a threshold and poses a risk to people.