Mountain pine beetles

The mountain pine beetle, Dendroctonus ponderosae, is native to the western United States. Like many of our pests (e.g., grasshoppers, army cutworms, Russian wheat aphids, etc.) in the High Plains and Rocky Mountain regions, these insects can go through outbreak periods. During the past couple years these regions have suffered from devastating numbers of this insect attacking pine trees. The symptoms can be easy to spot...

When the beetles enter a tree, the burrow they create results in the formation of a "pitch tube"; the results of tree sap exudate (see above). The above tree has been attacked many times and there are many exit holes in the pitch tubes. However, this sapping process is part of a tree's defense system and if the tree is healthy...

It will actually drive the insect out of the burrow, entrapping it and ejecting it from the tree (see above)...

A very healthy tree can defend itself well against numerous pine beetle attackers (see above). If you examine a pine tree with a few pitch tubes with beetles in them, there is a good chance the tree will survive that year's attack and some insecticidal treatments and tree-health improvements could save the tree. However, if a tree has many pitch tubes without any beetles, it is likely that the tree is not going to survive and should probably be removed.