A Douglas-fir tree struck by lightning in Columbia County. Photo: Oregon Department of Forestry

The Oregon Department of Forestry says the 2021 ice storm, which brought down many large-diameter Douglas-firs across the state created the potential for an outbreak of the native Douglas-fir beetle.

Christine Buhl, a Department of Forestry entomologist, said tree stands with pre-existing stress from drought, root disease, or other causes, are the most at-risk for a beetle outbreak, which tend to last one to three years before collapsing on their own.

“During that time beetles can move from downed wood to healthy Douglas-fir trees nearby, weakening or killing them,” Buhl said. 

Douglas-firs infested with the beetle present with an orange, sawdust-like powder on their bark, a sign that beetles have moved in and are preparing to lay eggs. 

Treatment includes finishing before April 2021 the removal of damaged material on trees and-or the application of MCH repellent, an anti-aggregation pheromone that is “effective, inexpensive, and sold as a general pesticide online,” Buhl said. 

“MCH won’t work for trees that have already been infested, so landowners need to act before an outbreak gets going,” she said.

For more information about the Douglas-fir beetle go to https://bit.ly/3u5FZLP

More about storm damage management is available at https://bit.ly/3avieos

The state of Oregon and the U.S. Department of Agriculture both released information on using MCH to protect trees and stands from Douglas-fir beetle infestation.