State and local forestry officials said Wednesday the emerald ash borer was found in an ash tree on private property.
Longmont officials said they would step up treatment of ash trees on city property and advised homeowners to have their trees checked.
The Emerald Ash Borer Information Network says the beetle has killed hundreds of millions of trees since it was detected in North America in 2002. It's been found in 26 states and two Canadian provinces.
It was detected in Boulder in 2013. Until now, it hadn't been found anywhere else in the state.
Officials said they didn't know how the beetle got to Longmont.