How does mountain pine beetle kill trees?
During late summer, adults leave dead trees and seek out and attack living green trees. They bore through the bark to get at the phloem the sweet juicy region that carries sugars from the pine needles to tree roots. Here they create galleries for their eggs. Eggs hatch within a few days and larvae mine outwards from the parent gallery girdling the tree. Adult beetles like to attack large-diameter trees. Bigger trees provide higher quality food and larval habitat than smaller trees and their thicker bark provides greater protection from predators and climatic extremes. However, large-diameter trees in a stand tend to be more vigorous and have a greater capacity to resist attack. As beetles try to bore through the bark of healthy pines, the tree produces large amounts of resin as a defense. The tree may overcome attacking beetles and literally ‘pitch’ them out as seen here. The beetles also carry spores of blue-stain fungus in their mouths. As they chew on the tree fungus spills out and
