Forest Health Issues in Southeast Colorado

Aside from a respite over the summer, forests across many parts of southeast Colorado experienced drought conditions last year, further weakening the defenses in trees from forest pests.

Counties most impacted in southeast Colorado in 2024: Custer, Fremont, Huerfano, Las Animas, western Pueblo

Piñon Ips beetle (Ips confusus) remains on the list of top forest health issues in southeast Colorado for the fourth year in a row. This native beetle targets piñon pine trees that grow in low elevations from 4,900 to 8,000 feet, where conditions are often dry and precipitation levels can fluctuate.

Piñon pine trees in Huerfano County, Colorado — These piñon pine trees with reddish-brown needles in Huerfano County are infested with piñon Ips beetles. Photo: Abbey Bowser, CSFS

This beetle is especially active in central Huerfano County north of U.S. Highway 160 where infestations persist. Other areas of concern for piñon Ips beetle include lowland piñon-juniper forests in Custer, Fremont, Las Animas and Pueblo counties.

Residents and land managers should remove trees infested with piñon Ips beetle as soon as they are identified – noting that it is best to cut and remove infested trees from November to February when beetles are inactive. It is also good practice not to stack infested wood next to living trees. The resin from cut trees attracts the beetle, so it is important to remove all freshly cut materials that result from pruning or thinning trees.

Also, landowners with piñon trees should time cutting activities when daytime temperatures fall below 50 degrees Fahrenheit, when beetles are unlikely to search out new material. Piñon trees should be watered during periods of drought throughout the year and insecticides can be used prior to attack, twice a year, as preventive measures for high-value landscape piñon trees.

Learn more ways to manage for this insect in the Piñon Ips Bark Beetle Quick Guide.

Counties most impacted in southeast Colorado in 2024: El Paso, Park, Teller

Colorado State Forest Service foresters from the Woodland Park Field Office continue to see impacts from the mountain pine beetle (Dendroctonus ponderosae) at high levels along the margins of the 2013 Black Forest Fire. Most of the beetle’s activity occurs along the eastern edge of the fire where fire-damaged and water-stressed trees are susceptible to attack.

A close-up image of mountain pine beetle pitch tubes — Pitch tubes from mountain pine beetle attack are present on the bark. Trees release resin to prevent beetles from boring through their bark, creating pitch tubes. Photo: Dan West, CSFS

Along with the Black Forest, small pockets of mountain pine beetle are also popping up in Teller and Park counties in southeast Colorado. While mountain pine beetles attack a variety of pine species, they are primarily impacting ponderosa pine in El Paso and Teller counties. Limber pine, a five-needle higher-elevation species, is the dominant tree species affected in Park County.

Colorado State Forest Service foresters help landowners identify infested trees and provide strategies to curb the spread of this beetle. Removing infested trees before the beetles take flight in the summer is an effective means to curb their spread. On a local scale, insecticide sprays and semiochemical treatments can prevent trees from being attacked.

Counties most impacted in southeast Colorado in 2024: Costilla, Custer, Huerfano, Park

Spruce beetle (Dendroctonus rufipennis) is new to the list of notable forest health issues in southeast Colorado. Once the deadliest forest pest in Colorado as recently as 2022, this native bark beetle is not at epidemic levels in this part of the state. However, aerial survey data and on-the-ground reports from Colorado State Forest Service foresters note the presence of spruce beetle in the Wet Mountains and the Culebra Mountains in western Las Animas County. Spruce beetle has also moved into the Mosquito Range in western Park County as it progresses north from the Collegiate Peaks.

dead trees suffered major blowdown in a mountain setting. — A powerful wind event in 2022 knocked over mostly spruce and fir across miles of the Sangre de Cristo Range. This windthrow provides a site for spruce beetles in the area to build their population. Photo: Jared Fleming, CSFS

A native insect, spruce beetle is a part of the forested ecosystem in Colorado, typically infesting Engelmann spruce and occasionally Colorado blue spruce in high-elevation forests. Populations of this insect tend to increase following avalanches or windthrow events.

In winter of 2022, one such windthrow event occurred on approximately 1,260 acres of high-elevation Engelmann spruce-fir forests in Costilla, Huerfano and Las Animas counties, specifically around the Bear and Blue Lake campgrounds within the Upper Cucharas River watershed. This area has an active spruce beetle population, so CSFS foresters have conducted work in this area to mitigate the beetle’s spread, including removing wildfire fuels out to 250 feet on either side of the road, and clearing fallen trees in campgrounds. The CSFS is planning more work in this area in 2025.

Counties most impacted in southeast Colorado in 2024: widespread

Western spruce budworm (Choristoneura occidentalis) is the most widespread forest pest in Colorado, so it is not surprising that it remains impactful in this part of the state. This insect infested 26,000 acres of forests in Park County alone last year, plus 5,100 acres in Las Animas County.

A treated stand of Douglas-fir trees in Colorado threatened by the western spruce budworm — CSFS foresters treated this stand of Douglas-fir to curtail an outbreak of western spruce budworm. The stand was thinned to create a residual, open structure and one canopy layer. Photo: Mike Tarantino, CSFS

The western spruce budworm has a one-year life cycle and is a small moth at full maturity. During its caterpillar stage, the budworm partially consumes the needles of Douglas-fir, true fir and spruce trees. The foliage turns a rust/burnt color and trees are at high risk of attack by the Douglas-fir beetle.

Douglas-fir beetle (Dendroctonus pseudotsugae) is also a species of concern for southeast Colorado with significant infestations in Freemont, Custer and Costilla counties.

Please refer to the map of insect and disease activity with current data from last year’s aerial survey to see specific locations where the budworm and Douglas-fir beetle are impacting forests.