The Mountain Pine Beetle (MPB) is an insect native to the forests of western North America. The beetles develop in pine trees, particularly in our Ponderosa pines. During early stages of an outbreak, beetles attack trees that are under stress from overcrowding, injury, or old age, but as MPB population increases, attacks may involve large healthy trees.

A tree that has been attacked will show the following signs:

MPB have a one-year life cycle in Colorado. In late summer the adults fly to live green trees, tunnel under the bark, mate and produce about 75 eggs per female. The larvae spend the winter under the bark, continuing to feed until they hatch into adults and exit the tree beginning in early July through September.

Once MPB infest a tree, nothing can be done to save it, and the beetles from that tree can kill nearby trees the following year. Trees infested with MPB should be cut, chipped, peeled or burned only January through May and October through December to minimize beetle attraction to freshly cut wood during the summer months. Remove slash from the site. Do not stack freshly cut wood against living trees; beetles may be attracted to the wood and attack the standing living trees. Cutting live trees is not recommended during the summer.

Infested trees can also be solar treated during the same non-summer months. If this treatment is begun after April 15, unstacked logs must be covered with clear plastic; otherwise plastic is not needed. The logs need to be in an area receiving direct sunlight several hours a day for 2 months.

Prevention is best done by thinning the forest and keeping the trees healthy. Healthy trees are able to withstand a beetle attack. Tree crowns of Ponderosa pines should be X feet apart. Woodpeckers and certain insects that feed on MPB as well as extreme cold temperatures also help to control infestations. Chemical control is not recommended because of the damage done to beneficial insects.

More information can be found at the Glacier View Demonstration Garden information box.