What are mountain pine beetles?

The mountain pine beetle (Dendroctonus ponderosae) is a native beetle – about the size of a grain of rice – that resides beneath the park of several species of pine trees. Mountain pine beetles play an important role in forest health by attacking old/weak trees and promoting the growth of younger trees. Unusually dry conditions and generally poor forest health, however, have led to recent infestations of otherwise healthy trees.

Approximately 4 million acres of Colorado’s lodgepole pine (Pinus contorta) forest were affected by a mountain pine beetle epidemic that began in 1996. The Colorado State Forest Service is currently monitoring another potential outbreak in both Gilpin and Clear Creek Counties, specifically Black Hawk and Idaho Springs, as well as increased activity near Colorado Springs (El Paso County). The current outbreak is affecting primarily ponderosa pines (Pinus ponderosa).

Identifying and Managing Beetle Infestations on Your Property

In this video, CSU Extension Gilpin Director Jennifer Cook describes what to look for on your property, as well as what to do when an infestation is confirmed. (Note: this video was filmed in November 2023.)

To summarize: First, survey the trees on your property, focusing on ponderosa (Pinus ponderosa), lodgepole (Pinus contorta), and limber (Pinus flexilis) pines. Dead trees (i.e. trees whose needles are all brown) no longer contain live beetles and should be removed for safety and/or fire mitigation. Next, look for pitch tubes on green (i.e. live) trees. Pitch tubes look like popcorn resting on the outer layer of bark, but they’re actually globules of sap and are a sign that the tree is attempting to flush the beetles out. Live infected trees (i.e. trees with visible pitch tubes and green needles) should be cut down as soon as possible – ideally before spring when the beetles fly. Once cut down, there are two ways to proceed. Debarking the tree will dry out the tree, killing all active beetles and larvae and preventing further infestation. Live infected trees (including slash) can also be mulched/chipped, which will again kill all active beetles and larvae. For trees that have not yet been infected, pheromone and pesticide options are available (links below).

In this webinar, Gilpin CSU Extension Director Jennifer Cook and Ben Pfohl of the Colorado State Forest Service discuss the mountain pine beetle that is affecting ponderosa and lodgepole pines in Gilpin County. Topics include tree identification, mountain pine beetle life cycle, treatment options for infested trees, preventative management options, local infestation locations, a comparison between mountain pine beetles and ips beetles, and a look at big picture forest health.

Gilpin County Resources

• Evergreen Identification Key for Gilpin County – flow chart style key for identifying and differentiating shrubs and trees present within Gilpin County
• What to do with your infested trees – CSU Extension Gilpin County
• Gilpin Public Works – Trash Transfer Station, Recycling, Slash – call ahead to make an appointment to drop off beetle infested trees/slash [2024 Slash Site info (pdf)]
• Mountain Pages (Summer/Fall 2024) – contact tree services listed within for assistance with removing live/dead infested trees and for preventing further infestation
• Timberline Fire Protection District – request a free wildfire property assessment here; mitigation services are available at reduced rates
• Contact the Gilpin County CSU Extension office to arrange a site visit: (303) 582-9106 or Jennifer.Cook@colostate.edu

Options to Protect Your Trees from MPB Attack

• Research on how to protect your trees from pine beetle – what works, what doesn’t – information on pheromone and insecticide treatment options
• Using Verbenone to Protect Host Trees from Mountain Pine Beetle Attack (pdf) – position paper by Ken Gibson, USDA Forest Service, FHP, Missoula, MT (January 2009)
• Purchasing Pheromone Packets: Beetle Block, Synergy Shield Verbenone Pouches and Bubbles, Forestry Distributing, Verbenone & MCH Express

Additional Resources

• 2023 Report on the Health of Colorado’s Forests – this report is published each year by the Colorado State Forest Service (CSFS) to provide both the general public and the Colorado General Assembly updates on the state of our forests
• Mountain Pine Beetle quick facts – CSU Extension
• Mountain Pine Beetle – Colorado State Forest Service (CSFS)
• Mountain Pine Beetle Frequently Asked Questions (pdf) – South Dakota Department of Agriculture and US Forest Service
• A Year in the Life of a Mountain Pine Beetle (pdf) – an illustrated booklet/coloring book written by Buford the Mountain Pine Beetle – great for kids!
• Bark Beetles, They’re Back! Are Your Trees At Risk? – a step-by-step guide for property owners created by the USDA Forest Health Protection offices in Ogden, UT, and Boise, ID, in cooperation with the Caribou-Targhee and the Bridger-Teton National Forests