But there's another tree-munching insect that's causing trouble in the Bitterroot Valley by taking advantage of the growing number of new residents who mistakenly thin their pine stands in the spring.
The pine engraver beetle is native to western Montana, but it appears to be spreading in the Bitterroot by feasting and laying eggs in logging slash piles each spring.
He said the insects are a significant problem on less than 10 percent of the Bitterroot's forests, but that their population appears to be increasing.
Unlike the mountain pine beetle - which turns whole hillsides of evergreens a rust color - the pine engraver beetle leaves dead trees in isolated patches.
“These beetles don't respect property lines,” Gelderman said. “They're opportunists looking for their next meal. It's almost guaranteed you'll see them if you create a slash pile at the wrong time of the year.”
Gelderman attributed the beetle boost to the Bitterroot's landscape being increasingly divided into smaller parcels by new landowners who aren't familiar with when and how to manage their trees.
He said educating new landowners is a continual task.
“We encourage thinning and we try to target people who want to do something to improve their forests, but they're not sure how and when to do it,” he said.
When the weather warms up, many landowners take up outside chores, including cleaning up broken and bent pine trees left over from winter storms, and thinning pine stands to try to create healthier forests and reduce wildfire hazards.
But those slash piles inadvertently invite infestations by the pine engraver beetle, also known as the ips beetle after its scientific name.
The beetle is attracted to the moist layer between the bark and the wood of downed logs and large limbs.
Piles of limbs and logs can quickly become infested by the beetles, which reproduce and create more beetles that emerge in the summer and fly off in search of food, said Sue Macmeeken, forestry program manager for the Bitterroot National Forest.
If downed logs aren't available for the emerging pine engraver beetles, they will attack the narrow trunks and limbs at the tops of standing pines.
The tops of the trees typically die within a year, but the rest of the tree often dies as well because the stress makes them vulnerable to infestations by other beetles that attack the trunks.
Pine stands should be thinned in the late summer to early fall. The slash should be removed immediately or burned the following spring.
Also, freshly cut firewood should be left on the ground, turned periodically and dried out before being stacked, so it doesn't invite beetles.
More than 60,000 acres of the Bitterroot National Forest have trees that were killed by bark beetles in the last two years.
Most were killed by the mountain pine beetle, but the Western pine beetle and the pine engraver beetle also are culprits. Their main targets are ponderosa pines and lodgepole pines.
A telltale sign of the pine engraver beetle is frass, or the red-orange boring dust they leave, while mountain pine and Western pine beetles cause trees to emit wads of sap. Woodpeckers also are a sign of Western pine beetles, which they prefer over other beetle species.
Bark beetles are a natural part of the western Montana's ecosystem, killing off the weakest trees and making more room for healthy trees to grow.
But in recent years, large fires, drought and overcrowded forests have weakened many trees, making more food available for bark beetles and boosting their populations.
The largest groups of beetle-killed trees in the Bitterroot are on the West Fork and Sula ranger districts around the 2000 fires near Sula.
Patches of dead trees also are on the east sides of the Darby and Stevensville ranger districts in the Sapphire Mountains.
More information is available from the DNRC at 375-0412 and the Bitterroot National Forest at 363-7151.
Reporter John Cramer can be reached at 523-5259 or at johncramer@missoulian.com.
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