Emerald Ash Borer

What is EAB?

Emerald Ash Borer is a tiny beetle with a big impact. It attacks and kills ash trees, and it has been in Colorado since 2013. It was discovered in Littleton in 2023.

If you have an ash tree and do not treat it, EAB will eventually kill it.

Before and after: A road in Toledo, Ohio before and after EAB came through:before-and-after-of-trees-affected-by-the-Emerald-Ash-Borer

What are the impacts?

Ash trees make up about 15% of Littleton's tree canopy — roughly 45,000 trees, most on private property. Losing them would mean:

  • Less shade and beauty
  • Fewer benefits like clean air, stormwater control, and wildlife habitat
  • Dangerous dead trees that cost more to remove

Do you have an ash tree?

EAB only attacks ash trees, so start by identifying yours. Learn how to identify an ash tree.

identifying Ash trees

Not sure? Send photos of your tree's leaves, bark, and twigs to the CSU Extension office. They can help you identify it for free.

Treat it or remove it?

Treat if your tree is:

  • Healthy and vigorous
  • In a good location, such as providing shade, curb appeal, or other benefits
  • Worth the ongoing investment, since trunk injection treatments are needed every 2-3 years for the life of the tree

The City of Littleton recommends professional treatment with systemic insecticides. Learn about treatment options here. Store-bought home treatments are not considered effective.

Hiring a tree care professional?

  • Ask for a State of Colorado Pesticide Applicator License
  • Verify they are insured and ideally ISA-certified
  • Get multiple quotes
  • Check the City of Littleton's list of certified arborists

Remove if your tree is:

  • Already declining or unhealthy
  • In a bad location, such as under powerlines or too close to structures
  • Not worth the long-term treatment cost

It is safer and cheaper to remove an ash tree before EAB weakens it. Dead trees become hazardous and costly.

Replace with diversity

Removed an ash? Plant a different species! Diversifying Littleton's tree canopy protects us from future pest outbreaks.

Need help? Check out the City of Littleton Forestry Subsidy Program — the City offers financial assistance up to $500 for Emerald Ash Borer treatment, dead tree removal, and contracted tree plantings to help residents care for our urban forest.

How to spot EAB

Look for these signs:

  • D-shaped exit holes in branches, about the size of a pencil eraser
  • S-shaped galleries under loose bark
  • Thinning leaves in the upper canopy
  • Vertical bark splits
  • Shoots sprouting from the trunk

larvae patterns under tree barkadult borers pictured on top of a penny
Left image: EAB larvae create distinct S-shaped galleries under the bark of ash trees
Right image: Adult borers are about 1/2 inch in length and exit branches through D-shaped exit holes

Not all ash tree pests are EAB. The lilac ash borer is less harmful and leaves round holes instead of D-shaped ones. Additional information and visual examples can be found here.

Don't move firewood!

buy it where you burn it posterEAB came to Colorado in infested firewood from out of state. Burn wood locally to prevent spreading pests. You never know what pest you might be spreading.

 

 

 

Questions?

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