Mediterranean Oak Borer

Mediterranean oak borer (MOB) is a tiny brown wood boring beetle. Female beetles tunnel into many species of oaks and have recently been found in Oregon infesting Oregon white oak (Quercus garryana). Despite being a woodboring beetle, they do not eat wood. These beetles carry fungi (such as Raffaelea montetyi and Fusarium solani) with which they inoculate their tunnels to feed their young. These fungi clog water-conducting tissues and cause a wilting disease in susceptible trees. MOB is native to Europe, west Asia, and northern Africa (Algeria and Morocco) but established populations in Korea and United States (California and Oregon). In its native range it infests weakened or dying oak and beech tree species, outside of native its range it has been killing relatively healthy oaks in California and Oregon.

In California, widespread reports of dying valley oak (Quercus lobata) came from Napa and Sonoma counties in 2019. Large populations of MOB have likely been present there and killing trees since at least the early 2010s. MOB infestations have spread to adjacent Lake and nearby Sacramento counties. Blue oak (Q. douglasii) is also a known host. In California, a single attack was found in a severely distressed California black oak (Q. kelloggii) and another attack in Oregon white oak. California officials found that MOB is already established and too widespread to be eradicated from central California.

In Oregon a single beetle was first captured in a trap in 2018 at Chinook Landing near Troutdale. Another beetle was captured in a trap in 2021 near Woodburn. In 2022 across seven sites and four counties in the northern Willamette Valley, there were 21 beetles captured, 14 of which were in Troutdale. In 2022, two Oregon white oak trees (Quercus garryana) were found to be positive for MOB, one near Troutdale and another in Wilsonville. In 2023, approximately 30 infested trees were found in Wilsonville.

Oregon Department of Agriculture is monitoring the spreading of MOB, the alive detection is available here. Below figure is the habitat suitability maps that were generated by Maxent model, using occurrence data from its native areas, with predictors include both climate and non-climate variables. Here is the website for interactive view of habitat suitability:

https://gpzhu.github.io/mobInPacific/mob.html.