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.

Mountain Pine Beetle Fact Sheet


Dwarf Mistletoe is a common problem in Lodgepole pine forests of Colorado.  They are small, leafless, parasitic plants on the branches of trees and can spread one to two feet per year on closely spaced trees.  Mistletoe kills slowly by robbing the tree of food and water over time, with a relatively long life cycle of 6-8 years between infection and seed production, making it a long-term disease control situation.  If trees become heavily infested, they are then susceptible to secondary attacks by Ips bark beetles and twig beetles.

One of the first symptoms of dwarf mistletoe infection is a slight swelling of the bark at the infection site, as the parasite further penetrates the tree, witches brooms may start to form along with other branch deformations.  

For further information about Dwarf Mistletoe and management strategies, please refer to the fact sheet provided below.

Dwarf Mistletoe Fact Sheet

Other Fact Sheets:

Twig Beetle Fact Sheet

Ips Beetle Fact Sheet