Woodborers Now Killing Trees

Woodborers are a natural part of our forest ecosystem, typically playing a role in the nutrient recycling of dead trees by chewing through wood and aiding decomposition. However, it has recently been observed that they are actively attacking seemingly healthy conifers. Often, woodpeckers follow up these insect infestations by chipping off bark as they search for their next meal.

Several factors may be predisposing live trees to woodborer attacks, with recent drought conditions being the primary suspect. Other contributing factors include root disease, shallow or rocky soils, and fire. Identification of a woodborer infestation can be similar to that of bark beetles, but there are some differences. Look for Douglas-fir or western larch with green foliage and the bark chipped off by woodpeckers. You may also see wide galleries with no distinct pattern packed with red powdery sawdust (frass) underneath the bark. Most of this damage has been observed in western larch and Douglas-fir.

While it is unlikely that woodborers will become a major cause of tree mortality in the Inland Northwest, they have now been added to the list of potential agents to consider when encountering a dead tree. Root disease and bark beetles will remain the primary threats, but woodborers are an additional factor to be aware of.