Emerald Ash Borer

What is Emerald Ash Borer?

Emerald Ash Borer is an insect responsible for the destruction of millions ash trees throughout the United State and Canada. EAB was first found in the United States in the 1990s, originally thought to be from ash wood pallets or packing material from Asia. EAB was first discovered in Boulder, Colorado in 2013. Since then, it has spread to Longmont, Lafayette, Lyons Superior, Broomfield, Westminster, Erie (2021), Arvada, and Thornton (2022). In June 2023, the first confirmed case of EAB was discovered in Littleton. Ash trees comprise approximately 15% of Colorado's urban forest, with approximately 1.45 million ash trees in total.

What is the impact on Greenwood Village?

There are an estimated 1,100 ash trees on property maintained by the City of Greenwood Village. Staff closely monitors those trees for any sign of EAB infestation. 

In 2023, Greenwood Village is treating all ash trees on City maintained property that are at least 10" in diameter and in good condition. In total, this includes 388 trees. Trees among the treatment group tend to be approximately 14.5" inches in diameter while trees in the nontreatment group are much smaller, averaging about 4.6". Through this program, we hope to preserve the most valuable trees in the Village.

What can you do?

  1. Determine if you have an ash tree on your property. Visit Colorado State Forest Service for assistance with ash tree identification.
  2. If you have ash trees, 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 species. If you aren't sure, contract a certified arborist. 
  3. Recognize signs of EAB infestation. Property owners with ash trees should be on the lookout for thinning of leaves in the upper canopy, 1/8-inch D-shaped holes on the bark and vertical bark splitting with winding S-shaped tunnels underneath. 
  4. 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.
  5. Help prevent further spread of EAB. Don't move firewood! Do not transport ash or any hardwood firewood, or any other untreated ash wood products, to other locations. 
  6. For general questions on emerald ash borer, treatment options, or how to make decisions about your trees and possible diagnosis, Visit the CSU Extention-Araphaoe County website or contact at mastergardener@arapahoegov.com or 303-730-1920.