Counties most impacted in northeast Colorado in 2022: Clear Creek, Gilpin, Jefferson

Mountain pine beetle (Dendroctonus ponderosae) may be familiar to residents of northeast Colorado who lived here during the epidemic of this insect two decades ago. Once the state’s most deadly forest pest, the mountain pine beetle affected about 80 percent of pine forests in Colorado from 1996-2014.

While the epidemic has subsided, outbreaks of this native bark beetle still pop up in pine forests across Colorado, enabled by overly dense forests and ongoing drought conditions.

Colorado State Forest Service foresters are monitoring what could be the start of an outbreak of mountain pine beetle along the Interstate 70 corridor near Idaho Springs and Black Hawk, as well as increased activity of this insect in the northern Black Forest near Colorado Springs. This time around, this insect is affecting primarily ponderosa pines.

Education is an important strategy for managing the mountain pine beetle. The CSFS offers a fact sheet for homeowners, poster and storybook available to order online.

Prolonged drought conditions remain a top forest health issue for northeast Colorado, resulting in the decline and death of many species of trees at all elevations. A lack of adequate precipitation leaves trees stressed and susceptible to attack by bark beetles and other tree-killing insects. (For an example, read the mountain pine beetle section on this page.)

Tree decline and death from drought stress are compounded in forests experiencing additional issues with insects and diseases, primarily dwarf mistletoe.

Once trees die, they remain standing or fall, adding to and changing the arrangement of fuels on the forest floor, which can lead to intense, large wildfires under the right conditions. This has helped change the timing and duration of the wildfire season in northeast Colorado to one that poses a year-round threat.

Counties most impacted in northeast Colorado in 2022: Jefferson, Park 

The western spruce budworm (Choristoneura freemani) is the most widespread forest pest in Colorado, so it is no surprise that this native insect ranks as one of the notable forest health issues in this part of the state. The budworm is most active in western and southern Jefferson County and northeast Park County. 

The western spruce budworm affects Douglas-fir, true fir and spruce trees and thrives in dense and unhealthy forests. Once it partially consumes the needles of trees, the foliage turns a rust/burnt color and the trees are at high risk of attack by the deadly Douglas-fir beetle. 

Colorado State Forest Service foresters manage stands to have well-spaced trees thinned from below growing at uniform height to reduce the dispersal of the budworm in its caterpillar stage. This also lowers the risk of high-severity fire in those stands and allows other tree species not susceptible to western spruce budworm, such as aspen and pines, to thrive.