Counties most impacted in southwest Colorado in 2022: Chaffee, Gunnison, Hinsdale, La Plata, San Juan

Spruce beetle (Dendroctonus rufipennis) remains active in forests in southwest Colorado despite a decline statewide. In some areas, this bark beetle has depleted susceptible Engelmann spruce and is attacking lodgepole pine. It prefers large-diameter trees but is attacking and killing trees as small as 4 inches in diameter.

Colorado State Forest Service foresters in the Alamosa office have noticed impacts from the spruce beetle around Trinchera Ranch and La Veta Pass to the New Mexico border. Near Salida, spruce beetle has made its way over the Continental Divide and into the Chalk Creek drainage near the historic town of St. Elmo. Effects of the spruce beetle are newly evident in forests in the Needle and San Juan mountains within Hinsdale, La Plata and San Juan counties, indicating the range of this beetle is expanding.

CSFS foresters manage for spruce beetle by removing affected trees before an outbreak. The CSFS has continued a large-scale salvage effort on the Alpine Plateau between Gunnison and Montrose to curb a potential spruce beetle outbreak there. Another way to manage for spruce beetle is by placing pheromone packets on trees. These packets release a chemical that tricks beetles into thinking an otherwise healthy tree is already infested with beetles.

Counties most impacted in southwest Colorado in 2022: Chaffee, Gunnison

New pockets of mountain pine beetle (Dendroctonus ponderosae) activity are appearing in pine forests in parts of southwest Colorado. Localized infestations in ponderosa, limber and bristlecone pines in Chaffee County and in lodgepole pines in Gunnison County continue to expand. Colorado State Forest Service foresters in Alamosa have detected persistent pockets of mountain pine beetle activity near South Fork, in the Bonanza area and in Conejos Canyon near U.S. Forest Service campgrounds.

Since 2020, the CSFS and its partners have worked to curb the spread of mountain pine beetle in the Taylor Canyon in Gunnison County. They are removing infested trees before adult beetles can emerge and attack new trees, treating an additional 186 acres in 2022. Logs removed through the project will become wood products.

Counties most impacted in southwest Colorado in 2022: Dolores, La Plata, Montezuma, San Miguel

Roundheaded pine beetle (Dendroctonus adjunctus) is a native bark beetle that attacks ponderosa pine. It is often found working with several other native bark beetles to create a “bark beetle complex” that injures and kills trees. Compared to other beetles in the complex, it attacks later in the year in October and November, resulting in trees being under attack by multiple beetle species for much of the growing season.

Ongoing drought in southwest Colorado has stressed pine trees and created ideal conditions for roundheaded pine beetle to thrive. Its footprint continues to expand in The Glade area of the San Juan National Forest northwest of Dolores and the Cherry Creek drainage in western La Plata County. It is slowing in some areas as there are fewer suitable trees to attack, but the beetle remains active overall.

Counties most impacted in southwest Colorado in 2022: widespread

Western spruce budworm (Choristoneura freemani) is the most widespread forest pest in Colorado, so it is not surprising this insect is spreading in many spruce-fir forests across southwest Colorado. It is a major defoliator of Douglas-fir trees. Colorado State Forest Service foresters in all five field offices in this part of the state noted the budworm as one of the top forest health issues in their neck of the woods.

The budworm eats the needles of spruce and fir trees, so it benefits from periods of moisture when trees experience a spurt of new growth. Drought continues to grip this part of the state, though, and the combination of budworms consuming the needles and a lack of adequate precipitation has weakened trees and set the stage for outbreaks of bark beetles.