This summer, Colorado forests might see a large increase in an unwanted pest.
A mountain pine beetle upsurge has left forests across Colorado’s Front Range at high risk. The 2025-26 winter, which brought warmer-than-normal temperatures and drought, left summer conditions prime for the beetle’s spread, and now the same native insect that affected more than 3 million acres of forests in the early 2000s and 2010s is spreading once again.
The Colorado State Forest Service (CSFS) has found a 148% increase in the beetle’s presence between 2024 and 2025, with affected acreage climbing from 2,263 acres to 5,544 acres. That number is expected to rise further in 2026.
The pine beetles have primarily affected forests that are dense with ponderosa pine trees, which are particularly susceptible on the Front Range, just west of metro Denver. By killing trees, pine beetles can complicate wildfire behavior, increasing the danger in a highly populated wildland-urban interface area like the Front Range. Because it is home to countless ponderosa pine forests with large trees, the Front Range acts as a feeding ground for pine beetles, which typically attack trees with a diameter of six inches or more. Using data provided by the Forest Inventory Analysis, the CSFS found that 54% of trees per acre in the Front Range area meet the six-inch threshold, leaving the area vulnerable to attack.
“Residents, land managers, and stakeholders need to better understand the potential scenarios they will face in the coming years as mountain pine beetle populations expand, and how beetle-caused mortality might alter fire behavior and threaten values at risk,” the CSFS detailed in its 2025 report.
Pine beetles lay their eggs in trees in late summer through early fall. These eggs hatch shortly after, and the larvae dig tunnels into the tree until the spring. When spring arrives, and the beetles are adults, they leave and find new host trees. While the majority of adult beetles do not emerge from trees until mid-July, early sightings of beetles in their larval stages indicate they may take flight two to four weeks early, giving the beetles more time to feast on trees.
Colorado’s record-breaking winter was a catalyst for the beetle outbreak. A season that saw record-low snowpack totals and warm temperatures weakened trees and left them vulnerable to beetle attacks. A low snowpack leaves trees without ever-important moisture, making them a perfect host for pine beetles, which thrive in dry and hot weather. A warmer winter also means that more beetles are likely to have survived the season, giving them stronger numbers when they emerge.
As the beetles consume the tree, they spread a blue-stain fungus within it, starving the tree of water and nutrients. The combination of the beetle eating the tree and the fungus starving it ultimately kills the tree.
After a tree is killed, red needles fall to the forest floor as early as one year later. The forest landscape is highly impacted, leaving dead brown trees scattered throughout. The fallen needles also add surface fuel for fires, potentially contributing to increased fire behavior.
Colorado ski resorts that are known for their beautiful, dense forests will be altered by the beetle outbreak. With the loss of thick pine trees, tight tree runs can vanish. Standing dead trees can also become hazardous, forcing ski patrol to spend time looking for them. The visual impact may be the most significant, with beetles making formerly lush, green mountains look barren.
CSFS staff are working with local, state, and federal services to support residents and to fight the outbreak. Through forest health projects, the CSFS is helping landowners “protect high-value trees; reduce the number of trees in a stand to increase individual tree health, helping trees gain the resources they need to ward off attack; remove beetle-killed trees to reduce fuels or infested trees before adult beetles emerge and fly to new trees; and create forests with trees that are a wider diversity of ages and species.”
This summer, Colorado might move into an El Niño cycle, which could help reduce the likelihood of wildfires. However, it will take several years of adequate moisture to stop the beetles.
