In the Southwest, the insects that have wrecked destruction on most coniferous forests are the bark beetles. The deterioration and destruction of trees is due to the spread of blue-stain fungi and tree girdling resulting from the bark beetle's excavation of tree layers and channels.

Bark beetles destroy trees when they excavate from the outer layer to the tree's inner cambial layer to lay their eggs. When the eggs of these bark beetles hatch, the larva will hollow out more tree channels as they feed.

A blue-stain fungus is also introduced to a tree when bark beetles dig out more tree channels. The fungi will grow and interfere on the water transport system of the tree. When this happens, the tree will deteriorate and then die.

A tree can be attacked by several bark beetle species at the same time. The bark beetles will partition a tree by elevation with one species on top of another. Species of bark beetles found on trees that are severely infested include the western pine beetle, roundheaded pine beetle, mountain pine beetle, and other species of Ips.