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Source: County of San Diego
July 7, 2025 (La Mesa) -- To protect the public and keep mosquitoes from potentially spreading West Nile virus, which was recently detected in Rolando, the County is scheduled to conduct ultra-low volume, truck-mounted, pesticide-mist treatments this week. The spraying aims to reduce the number of adult mosquitoes on about 4,000 parcels in the community of Rolando, which includes parts in San Diego and La Mesa.
The treatments are scheduled to take place from 1 a.m. to 6 a.m. from Wednesday, July 9 through Friday, July 11, depending on conditions.
While the treatments pose a low risk to people and pets and the pesticide dissipates in roughly 20 to 30 minutes, residents may wish—as a precaution—to stay inside, keep pets and pet bowls inside, and close windows during the treatment.
More information, including a map of the treatment area, frequently asked questions, and contact information for Vector Control, can be found on Vector Control’s Adult Mosquito Control Information webpage.
County Vector Control truck treatments will use AquaDuet—a pesticide approved by the Environmental Protection Agency that poses low risks to people and pets, according to the County.
As recently reported, the County detected West Nile virus in mosquitoes collected in that area on June 24. Follow-up surveillance and testing revealed additional West Nile virus-positive mosquitoes nearby, which necessitates the spraying for adult mosquitoes to reduce the risk of the disease being spread to people.
Normal activities can be resumed 30 minutes after the treatment. Also, beekeepers and those with insects kept outdoors are encouraged to shelter hives and habitats during treatments. Beekeepers registered with the County’s Department of Agriculture, Weights and Measures can request to receive advance notice when pesticide spraying that may affect bees is applied to blossoming plants in their areas.
So far, there have been no reported human cases in San Diego County this year. In 2024, the County reported 2 cases. However, West Nile virus remains a potentially deadly threat. Some people who become infected can suffer fever with other symptoms, headaches, body aches, joint pains, vomiting, diarrhea, or rash. But in rare cases, West Nile virus can make people extremely ill and even kill them. If you have symptoms, seek medical care.
County officials said people should continue to follow the County’s “Prevent, Protect, Report” guidelines to protect themselves from mosquitoes. Those include finding and dumping out standing water around homes to keep mosquitoes from breeding.
Prevent mosquito breeding
Dump out or remove any item inside or outside of homes that can hold water—whether from rain or landscape irrigation. Those things can include plant saucers, rain barrels, buckets, garbage cans, toys, old tires and wheelbarrows. Mosquitofish, available for free by contacting the Vector Control Program, may be used to control mosquito breeding in backyard water sources such as stagnant swimming pools, ponds, fountains and horse troughs.
Protect yourself from mosquito bites
Protect yourself from mosquito-borne illnesses by wearing long sleeves and pants or use insect repellent when outdoors. Use insect repellent that contains DEET, picaridin, oil of lemon eucalyptus, para-menthane-diol, 2-undecanone or IR3535. Make sure screens on windows and doors are in good condition and secured to keep insects out.
Report possible mosquito activity and dead birds
Report increased mosquito activity, unmaintained green swimming pools, and other mosquito-breeding sources, as well as dead birds—crows, ravens, jays, hawks and owls—to the County Vector Control Program by calling (858) 694-2888 or emailing vector@sdcounty.ca.gov.
Go to San Diego County’s “Fight the Bite” website to learn how to prevent and protect against West Nile virus and mosquitoes.
For more information about West Nile virus, go to the County Health and Human Services Agency’s West Nile virus webpage.
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