Bark Beetle Battle

A severe winter storm in December downed trees across North Idaho, creating conditions that can lead to bark beetle outbreaks if not properly managed, according to the Idaho Department of Lands.

Downed trees can act as “beetle bait,” allowing bark beetle populations to rapidly increase. If left untreated, these beetles can spread to nearby healthy trees, causing widespread damage. IDL is encouraging landowners to take timely action to reduce risks.

Three primary bark beetle species in Idaho are attracted to downed timber: pine engraver beetle, Douglas-fir beetle and spruce beetle. Each species targets different tree types and requires different management timelines.

Pine engraver beetles infest downed ponderosa and lodgepole pine and develop quickly. Slash and damaged trees between 3 and 12 inches in diameter are most susceptible. 

Landowners should remove, burn or chip this material before June 2026 to prevent beetles from spreading to healthy pine trees. Pine engraver beetles do not commonly attack western white pine.

Douglas-fir beetles target larger Douglas-fir and western larch logs greater than 12 inches in diameter. These beetles develop more slowly, but unmanaged logs can become infested this spring. A new generation could emerge in April 2027 and attack surrounding trees. Management of Douglas-fir and larch blowdown should be completed by late winter 2027, the release said.

Spruce beetles infest large Engelmann spruce trees greater than 16 inches in diameter and follow a similar lifecycle to Douglas-fir beetles. Spruce blowdown should also be managed by late winter 2027.

The most effective way to reduce bark beetle infestations is to remove downed or damaged trees. When salvage harvest is not practical, landowners can reduce risk by burning or chipping slash and processing logs into firewood.

Firewood should be split, debarked and dried in a sunny area. Avoid stacking green, unsplit wood near live trees, especially in shaded areas. If chipping slash, do not place wood chips at the base of standing trees, as fresh material can attract beetles.

Older, dry logs are generally not a concern, as bark beetles are primarily attracted to fresh, green material.

Management strategies may vary depending on tree species, size and volume of downed material. For assistance, contact your local IDL Private Forestry Specialist at 208-267-5577 or [email protected].