SALEM, Ore. – Trapping for Mediterranean oak borer (MOB) this summer showed this new pest from Europe, North Africa, and western Asia is now present across the northern Willamette Valley in at least six counties – Clackamas, Marion, Multnomah, Polk, Washington, and Yamhill. MOB is a concern because it has infested Oregon white oaks, sometimes with fatal consequences. The tiny beetles carry fungi that can infect a tree with a vascular wilt, which can lead to tree death.
Before now, state and federal officials did not know how extensive Mediterranean oak borer’s presence in Oregon might be. Individual borers had shown up in traps here and there in the Willamette Valley even before the first infested Oregon white oaks (Quercus garryana) were found in Troutdale and Wilsonville. So this summer they set up traps all over the Willamette Valley and beyond to try and determine where MOB had reached.
What they found was that more than 500 of the tiny borers turned up in more than 30 traps on both sides of the Willamette River from the Portland area south to Salem. Catch rates varied from a single borer at a number of traps to 160 at a trap east of Oregon City. The borers were even caught in locations where no Oregon white oak trees had been reported declining…