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News Region

County sprays for mosquitoes with recent larvacide dumps


REGION — Last month, San Diego County began its annual larvicide dumps throughout the county to combat mosquitoes and diseases.

Chris Conlan, supervising vector ecologist, said the county is hopeful this year will show a decrease in West Nile, Zika, Dengue fever and other diseases spread by mosquitoes.

The county also conducts aerial drops from helicopters at 48 waterway sites throughout the county. The total 1,004 acres and will be done monthly for the rest of summer including on June 27.

The largest site is the Buena Vista Lagoon on the Carlsbad-Oceanside border, which covers 120 acres, followed by the San Elijo Lagoon (west and east) on the Encinitas-Solana Beach border spanning 80 acres.

“Those sites are chosen because they can’t be easily done any other way,” Conlan said. “There’s not good access or just too massive … whereas a helicopter can just cruise over and get done in a few minutes in what would take us an awfully long time.”

The larvicide does not hurt people or pets but kills mosquito larvae that eat the larvicide, before the larvae can grow into biting adult mosquitoes.

The list of waterways amounts to just more than 1,000 acres that stretch from Chula Vista in the south to Fallbrook in the north and from Oceanside in the west to Lakeside in the east.

The larvicide drops are just one part of Vector Control’s yearly mosquito-control program. County Vector Control also treats another roughly 1,400 potential mosquito-breeding areas each year by hand, gives out free mosquito-eating fish to the public, tracks down and treats neglected swimming pools, tests dead birds for West Nile virus and monitors cases for other potential mosquito-borne illnesses.

Last year, more than 50 cases of West Nile reported in the county, but just two were positive in humans. As for Zika, 108 cases have been reported from 2015 through June 1.

“For the aerial applications … that’s predominantly West Nile,” Conlan said. “The mosquito that can transmit Zika really doesn’t breed in those larger swampy conditions. The Zika mosquito, unfortunately, likes to breed in those smaller sources typically created in backyards.”

And while the county’s reach is substantial, it cannot spray into backyards and private property. Conlan said renters and home and property owners should be diligent in removing standing water to prevent breeding grounds for mosquitoes.

He said to dump out or remove any item inside or outside of homes that can hold water such as plant saucers, rain gutters, buckets, garbage cans, toys, old tires and wheelbarrows. Mosquito fish are another option and available for free by contacting the Vector Control Program. The fish may be used to control mosquito breeding in backyard water sources such as unused swimming pools, ponds, fountains and horse troughs.

Dates for aerial drops are as follows: June 27, July 18, Aug. 8 and 29, Sept. 19 and Oct. 10 (if needed). The dates are subject to change depending on trap counts.