The Mountain Pine Beetle – Should GVM Worry?

Almost everyone has seen or heard about the pine forest devastation occurring on Colorado’s western slope, especially in Summit County. Many GVM residents are concerned and have been asking what they can do about it on their own properties. This article is intended to provide information about your options for the prevention of Mountain Pine Beetle (MPB) attacks. This article is not intended to be a full education on the MPB and how they work. There are CSU handouts available at the GVM office and lots more information is available at . The following information comes from these publications.

The short story is that these beetles have a one-year life cycle in Colorado. Trees that are not growing vigorously due to old age, crowding, poor growing conditions, drought, fire or mechanical damage, root disease and other causes are most likely to be attacked. After tunneling under the bark, females mate and will lay eggs in vertical tunnels called "egg galleries". The MPB larvae spend the winter under the bark. They continue to feed in the spring and transform into "pupae" in June and July. Emergence of new adults can begin in early July and continue through September. However, the great majority of beetles exit trees during late July (lodgepole pine) and mid-August (ponderosa pine). Once MPB infest a tree, nothing practical can be done to save that particular tree. It is possible for a very healthy tree to reject the beetles and survive and attack. Trees from which MPB have already emerged do not need to be treated. The direction and spread rate of a beetle infestation is impossible to predict. However, attacked trees usually are adjacent to or near previously killed trees.

Should we worry? The answer is "probably not" since there is nothing we can do to control the flight plan of the mountain pine beetle (MPB). Should we take precautions? The answer is "yes" if you want to be proactive in protecting important trees on your property. An important method of prevention involves forest management. In general, MPB prefers forests that are old and dense. Managing the forest by creating diversity in age and structure will result in a healthy forest that will be more resilient and, thus, less vulnerable to MPB. Most mature Colorado forests have about twice as many trees per acre as those forests which are more resistant to MPB. Contact your local forester for more information on forest management practices. Thinning and pruning trees on your property is an important step toward creating healthier trees and a defensible space against wildfire.

Certain formulations of carbaryl (Sevin and others) permethrin (Astro, Dragnet and others), and bifenthrin (Onyx) are registered for use to prevent attacks on individual trees. These sprays are applied to living green trees in early summer to kill or deter attacking beetles. This preventive spray is generally quite effective through one MPB flight (one year).

Please call the GVM office for active service providers.