Lake County officials, scientists and tribes mobilize after Mediterranean oak borer kills mature valley oaks

Lake County supervisors heard an update Wednesday on the invasive Mediterranean oak borer and its rapid toll on valley and blue oaks across the county. Presenters from Cal Fire and the Clear Lake Environmental Research Center told the board that the insect has been confirmed in multiple counties and is killing large, older valley oaks—the county's keystone tree species.

The presentation said researchers, tribal environmental programs and county staff are expanding mapping and surveys, planning contractor and arborist training in early December, and lining up treatment trials and grant applications to slow the pest's spread. Tribal representatives urged the county to protect cultural resources and to monitor any pesticide work so it does not contaminate acorns or gathering sites.

Why it matters: valley oaks support thousands of species and are culturally important to local tribes, speakers said. County and federal aerial-survey figures cited in the meeting note large-scale tree mortality from multiple causes; presenters warned that Mediterranean oak borer could greatly increase oak loss unless community reporting, careful removal of infested wood and funded mitigation are scaled up.

Terry Logsdon, Lake County chief climate resiliency officer and tribal liaison, introduced the update and said representatives from Cal Fire, the Clear Lake Environmental Research Center and UC Cooperative Extension would present the latest findings. Cal Fire…