The Mediterranean oak borer (MOB; Xyleborus monographus Fabricius), an ambrosia beetle native to the Mediterranean regions of Europe, the Middle East, and North Africa, was detected in declining oak ( Quercus spp.) trees for the first time in North America in Napa County, California in 2019 (Fig. 1). Subsequently in early 2020, it was confirmed in the neighboring counties of Lake and Sonoma. Within its native range, MOB is a pest primarily of oaks, and one of its symbiotic ambrosia fungi, Raffaelea montetyi, has been shown to cause wilt disease in cork oaks in Portugal. In the California infestation, MOB was detected in valley oak ( Q. lobata) and blue oak ( Q. douglasii), and R. montetyi was recovered from both species.

Figure 1: Xyleborus monographus  adult & medium tip pencil. Photo by Curtis Ewing, CALFIRE.

MOB appears to initially attack the crown of host trees, where it can kill branches, with persistent infestations spreading to the main stem and eventually killing t he entire tree (Fig. 2). The extensive network of MOB galleries can weaken trees, making them more susceptible to failure. Thus far,  trees in California with MOB infestations appear to have been stressed by other biotic and abiotic factors prior to MOB infestations, so it is unclear if the insect and its ambrosia fungi can kill healthy North American oak species.

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After careful consultation with the CFPC executive committee regarding the health and safety of everyone in our industry and profession and communities, we have made the difficult decision to move the CPFC annual meeting from an in-person meeting to an interactive online webinar meeting. The meeting is still scheduled to take place on November 18th & 19th.

Due to the increased and overwhelming concerns about the COVID-19 virus, we felt this was the right decision during such an uncertain and unprecedented global situation. We are very disappointed that we are not to be holding this meeting in person; however, for the safety of everyone we feel this is the best alternative.