County to Conduct Two Mosquito Larvicide Drops This Week

The County’s Vector Control Program is scheduled to conduct two mosquito-fighting larvicide drops this week to help protect the public after recent heat waves and high tides increased mosquito populations in parts of the county.

On Wednesday, Aug. 8, Vector Control is scheduled to conduct its fifth regular aerial application of the summer, using a helicopter to drop batches of a solid, granular larvicide on roughly 48 rivers, streams, ponds and other waterways to kill mosquito larvae. Vector Control has conducted the aerial applications for many years to help protect people from mosquitoes that could potentially transmit West Nile virus.

Then, on Saturday, Aug. 11, Vector Control is scheduled to conduct a smaller larvicide drop on portions of Los Peñasquitos Lagoon and San Elijo Lagoon in Cardiff to reduce the numbers of saltmarsh mosquitoes — which aren’t capable of transmitting West Nile virus — that have increased because of high tides and high temperatures.

High tides can expand lagoon water into areas that are normally dry, creating new, hidden pockets of stagnant water where mosquitoes can breed when the tides recede. Hot temperatures, meanwhile, speed up the mosquito breeding cycle. The combination of having more places where mosquitoes can lay eggs and a faster breeding cycle has increased the numbers of biting adult mosquitoes.

County Vector Control is conducting the smaller, Saturday larvicide drop specifically to reduce the saltmarsh mosquito population.

The larvicide used by the County 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 that Vector Control treats aerially amounts to just over 1,000 acres, stretching 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.

Vector Control officials say the public also has an important role in fighting mosquitoes and mosquito-borne illnesses, and can help by following the County’s “Prevent, Protect, Report” guidelines.

Prevent mosquito breeding

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, available for free by contacting the Vector Control Program, may be used to control mosquito breeding in backyard water sources such as unused swimming pools, ponds, fountains and horse troughs.

Protect yourself from mosquito bites

Protect yourself from mosquito-borne illnesses by using insect repellent when outdoors, or by wearing long sleeves and pants. Use insect repellent that contains DEET, picaridin, oil of lemon eucalyptus, or IR3535. Make sure screens on windows and doors are in good condition and secured to keep insects out.

Report possible mosquito activity

Report increased mosquito activity, or neglected, green swimming pools and other mosquito-breeding sources, as well as dead birds — dead crows, ravens, jays, hawks and owls — to environmental health’s Vector Control Program by calling (858) 694-2888 or emailing vector@sdcounty.ca.gov. Also report if you are being bitten by mosquitoes during daylight hours, or if you find mosquitoes that match the description of invasive Aedes mosquitoes by contacting the Vector Control Program at (858) 694-2888.

For more information about mosquito-borne illnesses, go to San Diego County’s “Fight the Bite” website.


Gig Conaughton is a communications specialist with the County of San Diego Communications Office. Contact