County to treat Coronado neighborhoods for mosquitoes after West Nile detections

Verified: The County of San Diego announced scheduled ultra-low volume pesticide-mist truck treatments in Coronado to reduce adult mosquitoes; the County published the notice on September 22, 2026.

Observed fact: The County said the treatments will cover about 6,000 lots bounded by 2nd Street, Ocean Boulevard, F Avenue and Glorietta Boulevard; scheduled hours are 1 a.m. to 6 a.m. on Friday, September 25 and Saturday, September 26, with additional treatments possible the following week depending on conditions.

Source claim: County Vector Control identified elevated mosquito numbers in Coronado and reported some mosquitoes tested positive for West Nile virus; the County also reported 11 human West Nile virus cases in San Diego County as of September 16, 2026, including three Coronado residents; the County characterized this as the most local WNV infection since 2016.

Source claim: The County said it will use AquaDuet for truck treatments; the County described AquaDuet as EPA approved, as a pesticide that mimics natural insecticides found in chrysanthemum flowers, and as not posing a risk to people and pets when applied.

Practical consequence: Treatments are timed for early-morning hours to reduce public exposure; the County said the mist is practically invisible and dissipates in under 30 minutes. The County advised beekeepers and owners of outdoor insects and fish to cover habitats during treatments; registered beekeepers may request advance notice from the County Department of Agriculture, Weights and Measures.

Public guidance from the County: Follow its “Prevent, Protect, Report” steps. Prevent mosquito breeding by removing standing water around homes; use mosquitofish or mosquito dunks for backyard water sources. Protect yourself by wearing long sleeves and pants or using repellent; the County listed approved repellent active ingredients as DEET, picaridin, oil of lemon eucalyptus, para-menthane-diol, 2-undecanone and IR3535. Report increased mosquito activity, unmaintained green pools and dead birds to Vector Control at (858) 694-2888 or vector@sdcounty.ca.gov.

Support materials and access: The County posted a map, FAQ and contact information on its Vector Control Program Adult Mosquito Control Information webpage; the County also scheduled media availability for interviews between 9:30 and 11:30 a.m. on Friday, September 25 at the County Operational Center.

Analysis: Nighttime truck spraying reduces the chance people will be outdoors during application; it can lower adult mosquito numbers locally for a short period. The County did not provide an independent efficacy estimate or a quantified projection of how many human cases the treatments are expected to prevent; effectiveness depends on treatment coverage, mosquito species and ongoing local breeding sources. EPA approval and County assurances are relevant evidence; they do not, by themselves, guarantee zero risk to all non-target species or an exact public-health outcome.

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