Forest Health

The Mountain Pine Beetle (MPB) is a naturally occurring pest associated with mature, crowded, even-aged Lodgepole pine forests. The MPB does not respect property boundaries, so you must do mitigation work or preventative spraying to protect your high-value trees.

The MPB (Dendroctonus ponderosae) is an insect native to the forests of western North America. The MPB develops in pines, particularly ponderosa, Lodgepole, scotch, and limber pine. During the early stages of an outbreak, attacks are limited largely to trees under stress from injury, poor site conditions, fire damage, overcrowding, root disease, or old age. Presently, as the beetle population has increased, any tree larger than 4 inches in diameter is vulnerable to attack.

If a tree is attacked there may be popcorn-shaped masses of resin called pitch tubes on the trunk. These pitch tubes can be brown, pink, or white in color. Boring dust will also be present in bark crevices and on the ground immediately adjacent to the tree base and woodpeckers may be feeding on the beetles/larvae in the trunk actually de-barking the tree. Once a tree is infested with the MPB, even if it is still green, the tree cannot be saved. The summer following a successful attack, the pine needles will turn yellowish to reddish throughout the entire tree crown. By July, the adult beetles start to leave the dying trees, so after the first year, dead trees no longer harbor MPB. Under epidemic or outbreak conditions, enough beetles can emerge from an infested tree to kill anywhere from two to 10 trees the following year.

Management Information

In the long-term management, thin susceptible stands with emphasis on leaving well-spaced, healthy trees. In the short term, spray non-infested tree trunks with preventative insecticide sprays to protect trees from attack. Again, once a tree is attacked, nothing can be done to save the tree. It is best to remove an infested tree from your property, peel off the bark, chip the tree trunk, or mist all sides of the cut trunk with diesel fuel before July of the following year after infestation.

For preventative insecticidal tree spraying treatment, please be sure to hire a Colorado Department of Agriculture licensed applicator.