The Mediterranean oak borer (Xyleborus monographus), an invasive insect that primarily feeds on white oaks, was recently detected in Novato, prompting the Marin County Agricultural Commissioner and UCCE Marin to notify professional arborists and the public to keep an eye out for evidence of this invasive tree pest.
Joe Deviney, Marin’s Agricultural Commissioner, said the beetle – native to Europe, the Middle East, and North Africa – was identified in a valley oak on May 23, 2025. The insect was first detected in Napa County in 2019 and has since been found in nine counties.
“Education about the beetle is important, but unfortunately it can’t be eradicated and it’s becoming more widespread in our area,” Deviney said. “It was only a matter of time for the presence of this invasive pest to be confirmed in our county.”
Deviney’s staff is working closely with the Marin office of the University of California Cooperative Extension (UCCE), which has programs about agriculture and natural resources, forest health, horticulture, human-wildlife interactions, and others. Those County of Marin departments are collaborating with State of California pest management and wildfire agencies on efforts to detect, study, and educate about the borer.
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