Emerald Ash Borer: A Green Menace

Emerald ash borer (Agrilus planipennis; EAB) is a wood boring beetle native to Asia. It was introduced into North America during the 1990s, likely via shipping materials such as ash wood pallets or wood packing material.

Since its initial discovery in southeastern Michigan in 2002, this insect has killed millions of ash trees (Fraxinus spp.) throughout the central and northeastern United States and Canada. EAB is now considered the most destructive tree insect pest ever to be introduced into North America. Approximately 15 percent of the trees in Colorado’s urban forests are ash, making this insect a major threat to urban forests statewide.

EAB was first detected in Colorado in Boulder in September 2013. The entire city of Boulder was presumed infested by the end of 2015, and a federal quarantine was placed over Boulder County to curb the spread of EAB. In 2019, EAB was confirmed in Broomfield, outside of the federal quarantine, and in unincorporated Larimer County. The EAB quarantine around Boulder County was repealed effective Dec. 30, 2019.

Where is EAB in Colorado?

• EAB continues to spread along the northern Front Range.
• In 2023, EAB was detected in Carbondale. This is currently the only confirmed detection of EAB in western Colorado.
• The most recent confirmed detections were in Berthoud, Golden, Edgewater, Aurora, Denver and Wheat Ridge.