Adulticiding

Adulticiding:

San Mateo County Mosquito and Vector Control District takes a preventative approach to mosquito control. Whenever possible, mosquitoes are controlled in their immature stages, before they emerge as biting adults. To read about control of immature mosquitoes Click Here.

Truck-mounted Fogger

Occasionally, adult mosquito populations may reach high enough levels to become a threat to human health. When this happens, adulticides (materials used to control adult mosquitoes) may be applied to reduce adult mosquito populations. The decision to adulticide is based on surveillance information documenting levels of adult mosquitoes that may be high enough to pose a threat to human health. When application of adulticides becomes necessary, they are applied by licensed applicators and only in areas where high numbers of adult mosquitoes exist.

The material used to control adult mosquitoes contains Pyrethrum, a natural insecticide extracted from certain varieties of chrysanthemum flowers. It is applied at an ultra-low volume (ULV) from either hand-held or truck mounted equipment. Hand-held foggers are used to treat very small contained areas. Such cases usually occur when a broken sewer pipe has caused mosquitoes to develop unnoticed under a single building. On rare occasions, it may become necessary to apply adulticides from truck-mounted foggers. When truck-mounted fogging occurs, it is conducted in the early morning hours from 12:00 AM to 5:00 AM.

Adulticide materials used by the District pose very little risk to humans or the environment. They are applied at very low concentrations (typically less than 1 ounce per acre) in a very fine mist. Because of the extremely small size of the droplets in the mist, most of the material evaporates or breaks down before settling on surfaces. The fog dissipates in less than 15 minutes and any residue breaks down within hours. It is not necessary to wash off outdoor furniture or playground equipment before use.