County researchers, risk authority warn Mediterranean oak borer is spreading; officials outline detection, treatment and disposal steps

County and nonprofit researchers told the Lake County Board of Supervisors on Feb. 25 that the invasive Mediterranean oak borer (MOB) has expanded across much of the county and that early detection and careful handling of wood are essential to slow its spread.

The announcement came during a joint update from the Lake County Community Risk Reduction Authority, facilitator John VanderVoort and partners from the Clear Lake Environmental Research Center (CLEREC). RRA staff highlighted 2024 programming and outreach; CLEREC staff then gave a detailed presentation on MOB biology, symptoms and recommended treatment and woody‑material handling.

The RRA update: why this matters

John VanderVoort, facilitator for the RRA and Conservation Program Manager at the Lake County Resource Conservation District, told the board the RRA exists to coordinate preparedness and resilience work across cities, tribal governments, fire districts and other local agencies. He said the RRA held monthly meetings in 2024, launched a website and YouTube channel, convened two virtual town halls and formed subcommittees on biomass utilization and grants coordination. VanderVoort noted the RRA received adaptation planning grant funding (APGP) to support administrative staffing through 2025 and said finding sustained funding is a top 2025 priority.

“Between now and November of 2025, we will be hosting two additional workshops focused on providing DEI learnings to our leadership and members,” VanderVoort said, describing ongoing work to broaden participation and pursue funding and program continuity.

MOB: how to spot it and what to do

Julia Klicker, a biologist with the Clear Lake Environmental Research Center, presented the center’s Mediterranean oak borer action plan and walked the board through field signs to look for: tiny circular holes in bark, pale boring dust at the base of trees, black trellis‑like galleries in shallow wood layers and patchy dieback starting at branch tips. Klicker said those signs can be confused with drought stress, wind damage, bark beetles and sudden oak death, so photographic documentation and reporting are important.

Klicker summarized the beetle’s life cycle and risks: a single unmated female can found an infestation; females are capable of flight and can produce multiple generations a year in Lake County’s climate. She advised that pruning or moving infested limbs is safest during the beetle’s low‑activity months (roughly November through January) and that chips should be no larger than 1 inch in diameter if used on‑site. She warned that once galleries reach a trunk the tree can be girdled and pruning limbs will not remove the infestation.

Experts urge aging, chipping or burning — not movement

Michael Jones, a forestry advisor who has tracked the pest since 2020, told the board there is anecdotal evidence that certain fungicide treatments may slow decline in individual trees but that the research is not definitive and treatments are not practical at forest scale. He and other presenters emphasized that the biggest human pathway for spread is moving freshly cut oak or unprocessed wood. “By moving chips it can create a whole new infested area,” Klicker said.

Jones added local investigators have found trees that were infested in 2020 that are still alive, and that some treated trees appear to have limited damage, but he urged caution because it remains early to draw conclusions about fungicide effectiveness.

Local response and next steps

Presenters said CLEREC has created a public MOB reporting survey and dashboard to capture citizen reports and support follow up; the group plans public training for arborists and the general public, tracker tools for firewood transport and an open house Q&A. The RRA is pursuing grant funding including Community Wildfire Defense Grant applications that would fund detection and on‑site treatment projects if awarded.

Supervisor Sabatier and others asked about how owners and small firewood businesses will access heat‑treating or kilns. Will Evans, executive director of CLEREC, said the group is exploring partnerships, including a mobile kiln prototype developed with Cal Poly Humboldt partners, to provide localized treatment options. Several speakers urged education campaigns to discourage moving wood immediately after cutting and to encourage on‑site aging or chipping during the beetle’s low activity period.

Public and utility engagement

Representatives from PG&E said they are participating in vegetation management meetings and updating field crews on best practices to reduce spread. Multiple supervisors and local officials praised CLEREC and the RRA for coordinating outreach and thanked local experts who first alerted the county.

What the county will do next

RRA and CLEREC leaders said they will continue outreach, run trainings for arborists and the public, refine the reporting dashboard, pursue grant funding for treatment pilots (including a potential mobile kiln or burn unit), and work with partners to produce a countywide response plan. Board members asked staff to keep the county board updated on grant applications and any proposed emergency declarations.

Provenance: presentation portions of the RRA update and the Mediterranean oak borer presentation were given during agenda item 6.3; the RRA overview began with facilitator John VanderVoort and CLEREC’s presentation by Will Evans and Julia Klicker. Ending remarks and public comments followed the presentations.