PORTLAND, Ore. (KOIN) — An invasive insect from Europe and the Middle East that attacks oak trees has recently been found in several Oregon white oaks in Wilsonville.

The Mediterranean oak borer (MOB) is a tiny woodboring beetle that transmits multiple fungal species to the trees it infests. Some of these species may cause a disease called oak wilt, which can kill oak trees in as little as two to three years.

This insect was first found in North America when it turned up in 2017 in California, where it has been responsible for the decline and death of many native oak trees.

  • The Mediterranean oak borer is a tiny, reddish-brown beetle that can be confused with many other beetles that reside in oak.
    The Mediterranean oak borer is a tiny, reddish-brown beetle that can be confused with many other beetles that reside in oak. (Courtesy: Oregon Dept. of Forestry)
  • MOB create tiny, perfectly round entrance holes.
    MOB create tiny, perfectly round entrance holes. (Courtesy: Oregon Dept. of Forestry)
  • MOB galleries look like tiny black holes from the exterior of the wood.
    MOB galleries look like tiny black holes from the exterior of the wood. (Courtesy: Oregon Dept. of Forestry)
  • MOB galleries look like tiny black holes from the exterior of the wood.
    Pale boring dust is kicked out by the beetle and found on the exterior trunk of the tree. (Courtesy: Oregon Dept. of Forestry)
  • The tunnels Mediterranean oak borers dig look like black, branched trellises on the cut face of wood.
    The tunnels Mediterranean oak borers dig look like black, branched trellises on the cut face of wood. (Courtesy: Oregon Dept. of Forestry)

“MOB was found in a single trap set by ODF in Multnomah County, Oregon in 2018,” said Wyatt Williams, Oregon Dept. of Forestry (ODF) Invasive Species Specialist, “It was then found in traps in 2020 in Marion County, and in 2021-2022 in Clackamas and Washington counties. This spring it was found in a single Oregon white oak at Sandy River Delta.”

The Oregon Department of Agriculture said they and ODF have been in touch with their California counterparts to assess the impact of MOB on native and introduced oaks, while also exploring control measures.

In the meantime, to avoid spreading the insect pest, the departments of Forestry and Agriculture are asking people not to move firewood from oak trees beyond the local area where it is cut.

Landowners are asked to review the signs and symptoms of MOB (photos in the slideshow above) and report to the Oregon Invasives Hotline.