Come spring, bark beetles may attack damaged trees

Severe wind storms in North Idaho and the Spokane area on Nov. 17 did more than cause widespread damage to structures and power lines -- they made forested areas more susceptible to infestations of certain bark beetles next spring.

Idaho Department of Lands forest health officials want forest landowners to know that trees uprooted or broken in the storm can become infested by bark beetles once the weather warms up again, and what they can do now to minimize the chance for infestations. The beetles can build up populations in the damaged logs and then attack and kill neighboring healthy trees.

Ponderosa pine and lodgepole pine larger than 3 inches in diameter can be infested by the pine engraver beetle. Pine engraver beetles that infest wind-thrown trees in April and May will lay eggs that develop into adults and emerge in June of the same year. Beetles that emerge in June often attack adjacent live trees.

Douglas fir can be infested by Douglas fir beetle. Beetles infesting damaged Douglas fir in the spring will produce offspring, which could infest live trees in spring of 2017.

Both bark beetle species are highly attracted to the moist tissue under the bark of wind-thrown trees, broken tops, and logs.

The best option to reduce beetle infestations is to remove damaged trees. If there are not enough trees to economically salvage, consider safely burning or chipping, or removing branches and cutting green logs into smaller pieces.

Forest owners can hasten the drying of logs and green wood by placing them in a sunny area before beetles fly in the spring. Leaving damaged trees or decks of green logs in shady areas increases the chances that they will be infested. DO NOT stack green firewood next to live standing trees. The idea is to reduce the number of places for the damaging beetles to breed and then kill live trees.

Detailed information for forest landowners on how to manage pine engraver and Douglas fir beetles is available on the IDL website under “Hot Topics” at this link: http://www.idl.idaho.gov/forestry/forest-health/index.html