By Dr. Judith von Ahlefeldt, Landscape Ecologist
In Colorado, the conifer hosts for mountain pine beetles (Dendroctonus ponderosae) are ponderosa pines and lodgepole pines (mountains). Ponderosa pines are dominant conifers of lower timberline forests bordering the Great Plains, and extend east from the mountains, mostly on private lands.
Extra warm, mostly dry conditions and mild, short winters have supported major population increases in all bark beetles, especially mountain pine beetles, everywhere in Colorado. Other bark beetles that kill other species of conifers (spruce, Douglas fir, pinon pine) have all increased dramatically in the past two years statewide.
On Dec. 16, 2025, Colorado Gov. Jared Polis announced the formation of a special Mountain Pine Beetle Task Force and appointed its members in late February. The Task Force has three co-chairs: Dan Gibbs executive director, Colorado Department of Natural Resources (DNR); Matt McCombs, director of the Colorado State Forest Service, state forester; and Mike Morgan, director of the State Division of Fire Prevention and Control.
Mountain pine beetles are native insects, and usually have low (endemic) populations of a few infested trees in several to many square miles. Periodic epidemic population increases happen (of record, a few times a century per large areas).
Epidemics (may shift locations and last a decade or more) mostly last until there are no more suitable host trees, or populations are killed by extreme winter cold events. A week of extreme Polar Vortex 1981-82 stopped the 1977-82 epidemic in El Paso County.
On the first day of spring, 2026, there are still endemic (light) occurrences of mountain pine beetle-infested trees in western El Paso County and on the Palmer Divide west of State Highway 83 (per the 2024 Forest Health Report).
Prompt removal of ponderosas infested last season (summer, fall of 2025) is critical to prevent a likely exponential increase as the 2022 to 2024 ongoing epidemic-level outbreak of mountain pine beetle in the fire perimeter areas of Black Forest continues. These epidemic areas are still mostly in locally light burn areas of southeast and southcentral Black Forest ā but spreading.
Green ponderosa pines should be inspected now for still-pliable pitch tubes higher than 2-3 feet on tree trunks. Take bark samples with an ax to check for blue stain wood on the trunk. Successfully infested trees are faded but may wilt and fade soon in hot, dry weather. Mountain pine beetles prefer larger trees (14-inch diameter and larger but can infest smaller ones 8-13 inch diameter).
If the still-green ponderosa has pitch tubes AND blue stain in the trunk wood, it should be removed from the treed area before June to mitigate beetle populations.
Only the trunks need to be removed from the site for beetle infestation. Slash can be disposed of separately. Cut trees from close to the base to a 6-inch top stem diameter. Search āmountain pine beetleā.
Wood can be buried under 8 or more inches of soil, taken to Rocky Top Resources or to the Slash-Mulch site in Black Forest for 8-inch or smaller diameter logs cut into 6-foot or shorter lengths. It is too late in the season for plastic solar treatment, mastication, or pesticide application.
The Black Forest Slash/Mulch site opens May 2. See bfslash.org for details. There is a $10 per load dump fee. Rocky Top Resourcesā main wood recycling facility is located on East Las Vegas Street in Colorado Springs. For private landowners, the weekday dump fee is $25 per load, and on Saturday, private landowners are charged $10 per load. There is no diameter or length limit on logs. Landowners must unload all sizes and types of loads at Rocky Top, so infested trunks may need to be cut to short lengths.
Dr. Judith von Ahlefeldt can be contacted at judithvonahlefeldt@ocn.me.