Insecticides for Larval Mosquito Control
Mosquitoes can be controlled while in their larval developmental stage. Inspectors  conduct daily inspections to find the mosquito larvae and take the necessary action to kill them.  Small containers are emptied, while larger naturally occurring areas may require the use of an insecticide.  This process is known as larviciding, and while time consuming and labor intensive, it prevents the larvae from becoming flying, biting mosquitoes.

The primary insecticides used to kill mosquito larvae are Bti and Methoprene.  Each of these insecticides is approved for use by the Environmental Protection Agency, and used according to label directions.

Bti - Bti (Bacillus thuringiensis
israelensis) is applied in either liquid or granular form to areas of standing water with mosquito breeding.   The mosquito larvae eat the material, with death resulting in 8-12 hours.  Bti   affects only mosquito and blackfly larvae.  Other animal and plant life are not affected.
Methoprene – Methoprene (Altosid) is an insect growth regulator that is applied in liquid, granules, pellets, or briquets to areas of standing water with mosquito breeding.  This material prevents the mosquito larvae from emerging as viable adult mosquitoes.
 

Insecticides for Adult Mosquito Control
There are four insecticides used in the County's adult mosquito control program:

Fyfanon (Malathion) 97% concentrate is an oil based organic phosphate insecticide that is used in spray trucks. Although Fyfanon has a disagreeable odor, it is not irritating to the eyes or the skin, is relatively inexpensive, and relatively safe.
Bio-Mist 30+30 (Permethrin) is a synthetic version of Pyrethrin insecticide, derived from the Chrysanthemum. It will replace Fyfanon in the near future as the primary insecticide used in spray trucks. Rotating insecticides reduces the likelihood of insecticide resistance.
Scourge 4-12 (Resmethrin) is another synthetic version of Pyrethrin insecticide that is effective in controlling adult mosquitoes. It is used primarily in portable ULV sprayers used to spray yards to control localized mosquito populations.
Naled (Dibrom Concentrate) is an oil -based organic phosphate insecticide used solely for aerial application. It is highly effective in controlling adult salt marsh mosquitoes. It is somewhat irritating if droplets get onto the skin or in the eye.

Effectiveness and Safety of The Insecticides
The insecticides used are known as contact sprays. As the name implies, the insecticide must contact the mosquito in order to kill it. The insecticides do not prevent or repel mosquitoes from an area. Adult mosquitoes that migrate into an area after spraying are not killed, and it may sometimes appear that the spraying was ineffective.

The insecticides used to control mosquitoes are non-persistent. They last only a short period of time, and are biodegraded into harmless byproducts. All insecticides used are EPA approved, and used in strict accordance with label instructions.