As Emerald Ash Borer Emerge, Experts Warn Ash Tree Owners to Make a Plan

Emerald Ash Borer Adult – Photo courtesy of Dan West, CSFS

Around 15% of the trees on the Front Range are ash trees and they’re all at risk from Emerald Ash Borer larvae currently turning into adult beetles that will emerge in May and June ready to infest new ash trees. It’s Emerald Ash Borer Awareness Week and KGNU’s Hannah Leigh Myers spoke with two members of the Colorado Emerald Ash Borer Response Team about the current status of the EAB threat to Colorado’s trees and the most recent guidance to address the growing problem.


(Download Audio)

EAB has been detected in multiple cities and towns across the Front Range, most recently in 2020 in Arvada, Louisville and north of Fort Collins in Larimer County.

As property owners consider removing ash trees to prevent further EAB infestations, the Colorado Emerald Ash Borer Response Team is encouraging residents to look into replacing ash trees with verities well suited to the Front Range which will help diversify the tree population and build local tree resilience.

The Colorado EAB Response Team includes members from the following agencies and organizations: Colorado State Forest Service, CSU Extension, Colorado Department of Agriculture, City of Boulder, City of Fort Collins, Davey Resource Group, SavATree, The Keystone Concept, Colorado Tree Coalition and USDA Forest Service.

EAB Tips for Front Range Residents:

  • Determine now if you have any ash trees. Identifying features of ash trees include compound leaves with 5 to 9 leaflets; leaflets, buds and branches growing directly opposite from one another; and diamond-shaped bark ridges on mature trees. More information about ash tree identification, including a helpful app, is at
  • If you have an ash tree, start planning. Decide if the overall health of the tree and the benefits it provides merit current or future treatment, or if it would be best to remove and replace it with a different species. If you are not sure, contact your local CSU Extension horticulture agent or an ISA Certified Arborist. If you do plan to treat the tree, the CSFS offers recommendations for selecting a tree care company.
  • Plant trees. Replace ash trees in poor health with diverse species. The Colorado Department of Agriculture offers a database of registered nurseries and landscape contractors.
  • Recognize signs of EAB infestation. Property owners with ash trees should be on the lookout for thinning of leaves in the upper tree canopy, 1/8-inch D-shaped holes on the bark and vertical bark splitting with winding S-shaped tunnels underneath. Report suspect trees by calling the Colorado Department of Agriculture at 1-888-248-5535 or filling out their EAB Report Form at
  • Help prevent further spread of EAB. Do not transport ash or any hardwood firewood, or any other untreated ash wood products, to other locations outside the Front Range. Dispose of ash wood safely by chipping, composting, milling into lumber or taking to a landfill.

For more information about ash tree identification, the symptoms of EAB, treatment options and how to use ash wood, go to

Additional Resources: