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Clear Lake researchers map Mediterranean oak borer threat and launch county monitoring plan
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Summary
Clear Lake Environmental Research Center presented an action plan for monitoring and managing Mediterranean oak borer in Lake County, urging residents and tree professionals to report suspected infestations and avoid moving fresh firewood or unprocessed branches.
Clear Lake Environmental Research Center biologists outlined an early‑detection and response plan Tuesday after presenting evidence that Mediterranean oak borer (Xylosandrus moristatus / commonly called MOB in the presentation) has expanded countywide and is now a priority for local landowners and agencies.
“Black trellis systems in the shallow layers of the tree, tiny circular holes in the bark, pale boring dust around the holes and patchy dieback starting from the tips of the branch” are the principal symptoms to watch for, Julia Klicker, biologist at CLERC, told the Board of Supervisors.
Why it matters: Mediterranean oak borer feeds in oak wood and spreads a fungus that clogs tree xylem; repeated or heavy infestations can girdle limbs and kill trees. County officials said the pest has been detected broadly across Lake County and that early reporting and proper handling of cut wood are essential to slow spread.
What presenters recommended: CLERC urged residents and arborists to report suspect trees through a public survey and map on the organization’s website. The organization advised that pruning of infested limbs be done during winter dormancy (November–January in California) and recommended chipping material to pieces 1 inch or less in diameter, burning in permitted conditions, or heat‑treating (minimum 140°F for 60 minutes) rather than moving unprocessed firewood during active beetle seasons.
Technical notes: Presenters said female beetles can produce both males and daughters from unfertilized and fertilized eggs, allowing rapid local expansion; development from egg to adult can be 5–8 weeks so multiple generations can occur within a year. MOB tends to affect oak‑dominated stands and is most active in valley‑elevation oak ranges typical to Lake County.
Agency response and follow up: County Risk Reduction and RCD staff said they are seeking grant funding to build local treatment capacity, including options such as mobile kilns and portable incinerators, and will coordinate an open house for arborists and the public. Supervisor Paiske and others emphasized outreach to utility vegetation contractors after presenters said pruning and roadside wood piles have probably helped spread the beetle countywide.
Ending: County officials urged residents to avoid moving fresh oak wood off a property, to report suspect trees via CLERC’s survey, and to attend forthcoming Q&A sessions for landowners and arborists.
