Washington residents have reported uncharacteristically high numbers of dead and dying Douglas Fir trees to the Washington State Department of Natural Resources (DNR) this spring and summer. The culprits: drought and bark beetles.
The native bark beetle species do not normally have the capacity to kill live, healthy trees. Instead, they breed in dead or downed branches and then infest small diameter, thin-barked portions of trees that are stressed or dying from factors such as root rot, fire or drought.
Those traveling on highways in South Puget Sound and lowlands around Blewett, Sherman or White passes will likely spot the damage to Douglas Fir trees.
Washington has had several years in a row of hot, dry summer weather. Douglas Fir trees in particular have been heavily affected by these drought conditions, which showed similar — though less significant — signs of stress in 2012 and 2015. Some trees seem to be dying from drought alone. It is this stress and easy access into the trees that has allowed beetle populations to grow larger than seen in recent years.
DNR is currently flying aerial surveys across the state to assess the breadth of damaged trees. These annual flights help the agency better understand the extent of infestation and other forest health issues. Results will be available by November.
From KXLY News: https://www.kxly.com/news/bark-beetles-attacking-douglas-fir-trees-across-washington/779067968