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Mosquito district briefs Portola Valley on West Nile surveillance, yellow jacket and rodent services

June 25, 2026 | Portola Valley, San Mateo County, California


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Mosquito district briefs Portola Valley on West Nile surveillance, yellow jacket and rodent services
Brian Weber, district manager for the San Mateo County Mosquito & Vector Control District, briefed the council on the district’s services, surveillance and local workload. He said the district operates an in‑house laboratory for West Nile virus testing and that, in 2025, technicians visited 839 properties in Portola Valley with no West Nile positives detected.

Weber outlined the district’s primary services: mosquito fish distribution for manmade containers and pools, targeted larvicide products for seasonal or large water bodies, yellowjacket control (mostly ground‑nesting), insect and tick identification and advice, and rodent-inspection guidance — emphasizing nonchemical, prevention-focused approaches. He noted Lyme disease prevalence in collected ticks is roughly 1–3% in the County’s samples and described tick‑dragging surveillance methods on trails.

Why it matters: Council members and residents raised local concerns — creek maintenance, owl boxes for rodent control, and how mosquito control interacts with other permits (e.g., stream bed alteration) — and asked about response times, which Weber said average one business day for service contacts. Weber encouraged residents to use the district’s free services and promoted an open house scheduled for June 27.

Council discussion: Members thanked the district and asked operational questions about responses to seasonal ponds, mosquito fish suitability for rain tanks, tick sampling cadence, and yellowjacket removal techniques. Weber noted that if West Nile virus is found in a bird or mosquito sample, adult mosquito treatment (fogging) may be considered; the district had not fogged Portola Valley in more than five years.

Next steps: The council and staff agreed to share the district’s contact information with residents via the next town newsletter and to coordinate on stream/creek concerns that might require permits. Residents were encouraged to report dead birds and call the district for inspections.

Sources: Presentation and Q&A with Brian Weber, San Mateo County Mosquito & Vector Control District.

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