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WALS - Wide Area Larvicide Spraying

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Wide Area Larvicide Spraying (WALS) to control pesky mosquitoes in Bakersfield

Every spring through fall, Kern county residents are afflicted by unrelenting nuisance as well as disease transmitting mosquitoes. The situation has gotten worse since the introduction of Aedes aegypti [pronounced a-deez ah-jip-tie] in 2013. Since then Ae. aegypti has increased in its distribution across the county. This mosquito is also known as yellow fever mosquito and local residents call it an “ankle-biter.” Aedes aegypti can transmit diseases such as yellow fever virus, dengue virus, Zika virus, and chikungunya virus. Fortunately, we don’t have these diseases in Kern County so far.

As it stands now, it is impossible for us to check hundreds of thousands of households in our jurisdiction and treat all the possible habitats for Ae. aegypti. Therefore, along with asking residents to do their part, this year we are going to implement a new (to our district) method called Wide Area Larvicide Spraying (WALS), to try to control the nuisance Ae. aegypti mosquito population on a wider scale.

Larvicides are insecticide products that kill mosquito larvae in standing water sources. We will be using a biological mosquito larvicide product called VectoBac WDG that has an active ingredient Bacillus thuringiensis israelensis (Bti). Bti is a naturally occurring soil bacteria and is very target-specific and its toxicity is limited to mosquitoes and related flies. You can learn more about VectoBac WDG here and Bti here. We have also attached the Label and Safety Data Sheet for VectoBac WDG here for your reference.

HOW and WHY a "Wide-Area Larvicide Spray (WALS)" Treatment Will Be Conducted

WALS will be conducted during the night when people are indoors, to limit accidental exposure, even though Bti is non-toxic to humans, birds, pets, fish, etc. Other mosquito districts have noticed reduction in mosquito numbers after WALS application, so we are hopeful it will provide Kern residents some relief as well.