Insect and Disease Affecting Trees in the Bitterroot

Beetle damage in a forest.








Insect and disease related mortality in the forests of the Bitterroot Valley attract a good deal of attention. In recent years, the native mountain pine beetle has increased in our area, leaving the tell-tale pockets of dead red needled trees on our mountains. While the greatest concentrations of mountain pine beetle mortality are occurring in the southern part of our valley, the forecast is for an epidemic level rise in mortality, with more acres of ponderosa and lodgepole pine turning red.

This past summer of 2011, a large concentration of white pine butterfly made their presence known. The caterpillar life stage feeds on the needles of pine trees, causing some defoliation, but little lasting damage was done to our forest. There were a few pockets of trees in the lower Skalkaho pass which received more severe defoliation.

Two publications linked here can provide you more details about these two insect outbreaks. The Bitterroot National Forest staff is actively engaged in promoting improved forest health and providing additional protection for trees in campgrounds and at trailheads. For additional information about the mountain pine beetle, visit