An emerald ash borer
A dead adult EAB embedded in a piece of ash tree bark.

BROOMFIELD, Colo. – A score of cities and towns along the Front Range have already treated or removed more than 17,000 public trees in preparation for – or response to – the arrival of emerald ash borer (EAB), a highly destructive tree pest. These same municipalities also have already planted more than 17,000 ash replacement trees as part of their EAB management plans, and along with Boulder County have collectively spent more than $9 million on the management of a tree pest that in Colorado has thus far only been detected within Boulder County.

These figures, which provide only a conservative estimate of what Colorado’s cities and towns are doing as they ramp up community forest management efforts related to EAB, do not include any expenses or current actions HOAs or homeowners are similarly taking.

“The fact that our communities are spending so much already to prepare for EAB is telling,” said Keith Wood, urban and community forestry manager for the Colorado State Forest Service.

“It’s a good indicator that we all recognize the potential environmental and economic impacts of losing a significant portion of our urban tree canopy in the years to come.”

He says that with this week being National EAB Awareness Week, the interagency Colorado EAB Response Team wants to highlight the actions communities are taking in the state, and prompt homeowners, HOAs and other property owners – particularly along the Front Range and in northeast Colorado – to determine now if they have ash trees, watch them for symptoms and consider early management options for EAB. These may include removing unhealthy trees before they die and planting new trees near ash that could ultimately replace trees lost to the pest.

Urban & community ash trees at risk

Along with Boulder County, municipalities currently taking significant actions to manage or prepare for EAB include Arvada, Aurora, Berthoud, Boulder, Broomfield, Denver, Erie, Fort Collins, Golden, Lafayette, Lakewood, Longmont and Loveland. In addition to its urban tree management efforts, the City of Denver also is running a broad EAB awareness campaign under the tagline “Be a Smart Ash.”

EAB, a non-native pest responsible for the death of millions of ash trees in more than 30 states, was confirmed in the City of Boulder in 2013, and has since been detected throughout Boulder County. The exotic insect has become a concern for communities all over Colorado because an estimated 15 percent or more of all urban and community trees in the state are ash, and each year EAB can fly up to a half-mile to infest new trees. There also is the ever-present risk of the pest spreading much faster through human transport of firewood and other raw ash wood.

“As we head into summer and camping season, one of the best steps all of us can take is to not move firewood,” Wood said. “This all-too-common practice is one of the primary ways destructive tree pests like EAB are spread.”

For more information about ash tree identification and the symptoms of EAB, go to the CSFS EAB web pages. For EAB quarantine, reporting and chemical treatment information, visit the Colorado Department of Agriculture’s EAB web pages.

EAB tips for Front Range/Northeast Colorado 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. Information about an ash tree identification app for mobile devices is available at
  • If you have an ash tree, start planning. Decide if the overall health of the tree merits current or future treatment or if it would be best to remove and replace it with a different, non-ash species. If you aren’t sure, contact a certified arborist. If pesticide treatment is the preferred option, the applicator must be licensed by the CDA as a Commercial Pesticide Applicator.
  • 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 S-shaped tunnels underneath. Report suspect trees by calling the Colorado Department of Agriculture at 1-888-248-5535 or filling out the EAB Report Form at
  • Be aware of EAB imposters.  Other insects like lilac/ash borer, ash bark beetle and flat-headed apple tree borer may look like EAB or cause similar tree symptoms. For more information, visit the Colorado Department of Agriculture website.
  • Help prevent further spread of EAB. Do not transport ash or any hardwood firewood, or any other untreated ash wood products, to other locations. Boulder County and some surrounding areas remain under a federal EAB quarantine, allowing for significant fines for those who move untreated wood from the area.

The emerald ash borer (EAB) is a non-native, wood-boring beetle that is responsible for the death or decline of tens of millions of ash trees in the United States and Canada. This insect was first discovered in Michigan in 2002, and since then it has spread to at least 32 states, including Colorado. As a non-native insect, EAB lacks predators to keep it in check. EAB only attacks ash trees in the genus Fraxinus, but has also been documented infesting white fringe tree. Mountain ash and other tree species are not susceptible.

The Colorado EAB Response Team includes members from the following agencies/organizations: Colorado Department of Agriculture, Colorado State Forest Service, City of Boulder, Boulder County, Colorado State University Extension, Colorado Tree Coalition, Green Industries of Colorado, University of Colorado, USDA Animal and Plant Health Inspection Service and various Front Range municipalities.