Colorado Mountain Pine Beetle Outbreak Expands 148% in 2025

According to a recently released Colorado State Forest Service (CSFS) report, Colorado’s top forest health concern is a mountain pine beetle outbreak along the Front Range that expanded nearly 150% from 2024 to 2025, Colorado State University Warner College of Natural Resources reported (5-19-26).

The report highlighted the continued spread of mountain pine beetles and other forest insects during the second consecutive year of above-average temperatures and below-average precipitation. Trees across Colorado’s forests remain stressed following a record warm winter and low snowpack, with bark beetle and western spruce budworm infestations expected to intensify and expand.

“It’s getting tough to be a tree in Colorado. Heat and drought are stressing our forests, turning many areas into tinderboxes and making it harder for trees to fight off bark beetles and other insects,” said Matt McCombs, State Forester and Director of the CSFS. “We can’t control the weather, but we can work together to lower the risks these outbreaks create, protect high-value trees and manage fuels.”

The 2025 Report on the Health of Colorado’s Forests identified mountain pine beetle and emerald ash borer as the state’s most significant forest health threats. According to aerial survey data from the USDA Forest Service and CSFS, mountain pine beetles impacted 5,544 acres of pine forests across a nine-county Front Range area in 2025, compared to 2,236 acres in 2024—a 148% increase.

The affected Front Range forests include densely populated areas with elevated wildfire risk and large numbers of trees susceptible to the native insect. Trees weakened or killed by drought, insects, or disease can alter wildfire behavior if ignitions occur from lightning or other sources.

“What we’re seeing with mountain pine beetles along the Front Range isn’t cause for panic, but it is a reminder to stay vigilant and get to work,” McCombs said. “Using good science and strong partnerships, we can build forests and communities that are more resilient in the long run.”

The report also noted that emerald ash borer was discovered in six new Colorado cities and towns in 2025, marking the highest number of new detections in a single year since the invasive insect was first identified in the state in 2013. Approximately 15% of trees in Colorado’s urban forests are ash species, making emerald ash borer a significant threat to communities statewide.