Picture by Alma Shaw
Sonoma’s native oak bushes, a defining function of our panorama and cultural heritage, are in important hazard as a result of speedy unfold of the Mediterranean oak borer, a small invasive beetle. Please learn the next replace from Sonoma Ecology Middle’s Analysis and Restoration Groups, about this critical risk to a few of our most treasured bushes and the necessary measures you possibly can take to assist stop additional unfold.
The Mediterranean oak borer (Xyleborus monographus, MOB) is a really small invasive beetle which originated in Europe and North Africa, in areas surrounding the Mediterranean Sea. Of their pure habitat, the beetles serve an necessary ecological function by serving to break down wooden in bushes which might be already dying, aiding within the tree’s decomposition and the eventual return of its vitamins to the soil. In america, nevertheless, the beetle is a quickly spreading invasive species, aggressively infesting each wholesome and pressured bushes alike.
Feminine beetles tunnel into the trunks and branches of bushes to put their eggs and within the course of introduce a fungus which spreads via the tissues of the tree, blocking water and nutrient move. Additional injury from the beetles’ tunneling weakens and finally kills the tree over time.
Infestations of oak bushes in Sonoma County had been first confirmed in early 2020, and as of 2025, MOB has already killed a whole bunch of hundreds of oaks in Sonoma County. Native infestations are discovered primarily in valley oak and a few blue oak, however Oregon white oaks are additionally prone.
What you are able to do:
MOB spreads by pure dispersal of the feminine beetles and thru the motion of infested firewood, untreated wooden merchandise, and yard waste or mulch. The beetles are extraordinarily tough to detect as a result of they’re roughly 1/tenth of an inch, concerning the measurement of a sesame seed. Firewood particularly is among the best methods invasive species like MOB unfold. In relation to procuring firewood, all the time attempt to observe the rule “purchase it the place you burn it.” Ask your firewood vendor the place the wooden is from and if it isn’t native, or the origin is unknown, take into account acquiring your firewood some other place. Equally, keep away from bringing exterior oak mulch or untreated oak merchandise onto your property–ask what sort of wooden your mulch is and the place it was sourced.
Greatest practices for disposal of infested wooden embrace burning, burying, and chipping. Reducing wooden to chips smaller than one inch and composting wooden at temperatures above 160°F are each efficient methods to kill the beetle. If chipping and burning aren’t attainable, cowl the infested wooden with a tarp for at the very least six weeks in winter or six months in summer time to forestall the beetles from rising.
The most effective methods to guard your bushes is to make sure the general well being of your valley, blue, and Oregon white oaks this fall earlier than the leaves drop, and be alert for modifications subsequent season. Deep watering throughout prolonged dry durations and mulching round trunks may help scale back stress on the bushes. If attainable, have a professional arborist examine your bushes commonly, particularly in late spring and early summer time when the beetle’s exercise is at its peak. Look out for defoliated and browning crowns, small gallery holes, and beetle frass (sawdust-like waste pushed out of galleries). One other signal of infestation are darkish, moist wanting areas on the bark of the tree the place sap and moisture could also be seeping.
Sonoma County’s oak bushes and the ecosystems they help aren’t solely beloved for his or her magnificence, but additionally play a key function in sustaining biodiversity and storing carbon. Collaboration throughout our group is important to forestall additional infestation.
When you see indicators of MOB, take footage and make contact with an arborist or Sonoma Ecology Middle’s Restoration Crew at restoration@sonomaecologycenter.org. Moreover, chances are you’ll contact the Sonoma County Agricultural Commissioner’s workplace at 707-565-2371 or the California Division of Meals and Agriculture at their Pest Hotline at 1-800-491-1899.
Please report any suspected infestations to the College of California Agriculture and Pure Assets via their Mediterranean Oak Borer/Pathogen Complicated Illness Reporting Survey: https://ucanr.co1.qualtrics.com/jfe/type/SV_9zwapzQGP0m1HBH
For extra info, together with photographs of signs to observe for, go to the College of California’s Agriculture and Pure Useful resource web site on the Mediterranean oak borer: https://ucanr.edu/web site/mediterranean-oak-borer.
