Emerald Ash Borer (EAB)

Emerald Ash Borer (EAB) has been identified and confirmed in a small area of Arapahoe County, within the City of Littleton near the border with Englewood, Greenwood Village, and Centennial. Now is the time for residents to learn more, prepare and consider their options. Here is a roundup of information, resources and steps you can take to protect your ash trees and mitigate the spread of EAB.  

What is Emerald Ash Borer?

Emerald Ash Borer (EAB) is an invasive insect that infests and kills all North American true ash species (Fraxinus spp.) including green and white ash, and their cultivars such as “autumn purple ash,” a popular white ash variety in Colorado. 

The larval stage of EAB feeds under the bark of trees, cutting off the flow of water and nutrients. Infested trees gradually die over a period of approximately three to five years.  

Are my trees at risk?

If you have ash trees on your property or within your HOA, you will be impacted at some point.  

Click here to learn more about ash tree identification and the signs and symptoms of EAB.  

Eventually, all ash trees will need to be treated for EAB with insecticides, or the trees will need to be removed.  

The Colorado State Forest Service maintains data on impacted areas within the state, available here: https://csfs.colostate.edu/forest-management/emerald-ash-borer/ .  EAB was first discovered in 2013 in Boulder County. Since then, it has been identified in Broomfield, Larimer and Adams counties in 2019 and more recently in Erie and Thornton in 2021. In June 2023, the first confirmed case of EAB was discovered in Littleton.  

EAB is here: make a plan now if you have ash trees! 

What are my options? 

You have a decision to make as to whether you remove or treat your ash tree. Many factors play into that decision, from tree health to the size of your tree.  

Learn more about treatment options, how to dispose of infected wood, tree care, when to begin treatment, and EAB look-alikes. Download the Emerald Ash Borer Treatment and Planning Q&A  .

Why does this matter? 

On average, 15% of urban trees are ash trees. Healthy ash trees play an essential role in urban tree canopy health; they slow down stormwater runoff, provide much-needed shade and greenery, and help mitigate climate change by storing sequestered carbon. There are easy, proactive steps we can take to minimize urban tree canopy loss and mitigate the spread of EAB.  

Learn More  

For general questions on EAB, treatment options, or how to make decisions about your trees and possible diagnosis, contact CSU Extension-Arapahoe County at MasterGardener@arapahoegov.com or 303-730-1920.