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Counties First Larvicide Drop


Last updated 5/5/2016 at 7:13am

The County of San Diego plans to start its annual aerial drops of mosquito-fighting larvicide Wed. March 4, on local waterways.

The mosquito species that are native to San Diego County and can transmit West Nile virus don’t need a lot of water in which to lay eggs, and can breed in people’s backyards. But the call for public help has taken on added importance because of the appearance of two invasive Aedes mosquito species in the last two years.

A helicopter drops granular larvicide on 48 waterways around the county roughly once a month from May through October each year to combat West Nile virus by trying to keep mosquito populations down. The larvicide doesn’t hurt people or pets, but kills mosquito larvae before they can grow into adult mosquitoes that can transmit West Nile virus and other diseases.

The Aedes species are different from San Diego County’s native mosquitoes in appearance and behavior. They’re smaller in size, have distinctive black and white markings, are known as aggressive biters and — unlike our native mosquitoes that prefer to feed between dusk and dawn — like to bite and feed during daylight hours.

County officials urged the public to follow the County’s “Prevent, Protect, Report” guidelines:

Prevent mosquito breeding sites. Every week, dump out and clean containers that hold water inside and outside homes, from equipment to toys, flower pots, old tires, anything that can collect water. Fill plant saucers with sand or fine gravel so water won’t form pools where mosquitoes can breed.

Protect yourself from mosquito bites. Wear long sleeves and pants when outdoors. Use insect repellent, preferably one containing DEET. Make sure the screens on your windows and doors are in good condition, do not have holes or tears, and are secured to keep insects out.

Report if you are being bitten by mosquitoes during daylight hours, or if you find mosquitoes that match the description of the yellow-fever mosquito or Asian tiger mosquito, by contacting the Vector Control Program at (858) 694-2888 or

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