County workers to prevent mosquito-breeding with larvicide drops

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SAN DIEGO – San Diego County workers plan to drop the year’s second round of mosquito larvicide on local waterways Wednesday.

Vector Control workers will use a helicopter to drop batches of solid, grainy larvicide on roughly 48 rivers, streams and ponds throughout the urban parts of the county, officials said.

The total area covered amounts to about 1,000 acres of water, and much of it can serve as breeding grounds for mosquito populations.

The poison is not harmful for humans or pets, but is deadly for any mosquito larvae who consume it, killing them before they’re able to grow into blood-sucking adult mosquitoes, officials said.

County workers last dropped the poison on May 9.

In addition to the larvicide drops, County Vector Control also treats about 1,400 potential mosquito-breeding areas by hand each year, 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 for other potential mosquito-borne illnesses.

Officials encouraged San Diego County residents to prevent mosquito breeding by dumping any outside standing water, and to report increased mosquito activity, potential breeding sources — including unused, green swimming pools — and dead birds to the County Vector Control Program by calling (858) 694-2888 or emailing

Residents were also asked to report being bitten by mosquitoes during daylight hours and finding mosquitoes who match the description of the invasive Aedes species.

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