Emerald Ash Borer

What is the Emerald Ash Borer (EAB)?

The emerald ash borer insect is an invasive tree pest that was found in Boulder in 2013. It has not been found anywhere in Aurora at this time, but it is expected to spread. Over the next decade, this insect has the potential to destroy more of Aurora's urban forest than any other disease or pest in history. For more information about the EAB, click here.

What can I do to help prevent the spread of EAB?

1. Determine if you have ash trees on your property.
2. Consult with a tree professional about proactively treating or removing ash trees.
3. Regularly inspect existing/remaining ash trees for signs of the EAB.
4. When removing ash trees, chip the wood smaller than one inch.
5. Do not transport ash tree remains.
6. Use local firewood only.

How do I know if I have an ash tree on my property?Identifying an ash tree is as easy.

1. Opposite Branching

Only ash, maple, dogwood and horse chestnut trees have opposite branching which means that branches have a mate protruding from the exact opposite side of the same limb.

Opposite Branching

2. Compound Leaves
A compound leaf has more than one leaflet per leaf connecting to a stem that has a bud at its base. Ash tree leaves typically have 5-9 leaflets per leaf.

Compound Leaves

3. Diamond-pattern Bark
While young ash trees often have smooth bark, the bark on established ash trees have distinct diamond patterns.


 Diamond-pattern Bark

Are all ash trees at risk?

Yes. The EAB is a threat to all common ash trees, including white, green, black and blue ash trees.

How can I tell if my ash tree has been attacked by the EAB?

It can take 2 – 4 years for ash trees to show signs of EAB infestation. Look for any combination of the following signs that your ash tree has been infected.

Tiny, D-shaped exit holes visible on the tree trunk.

 D Shaped Holes

Bark shredding and S-shaped tunnels on the trunk and under the bark.

 S Shaped Tunnels

Limb and leaf thinning.

 Limb and Leaf Thinning

Northern Flickers are large brown woodpeckers that are attracted to dying ash trees.

 Northern Flicker

Can my ash tree be saved?

Yes! Aurora residents who want to keep their ash trees should work with a licensed and insured arborist or tree service company on a pesticide treatment plan, which can be up to 90 percent effective. Treatment must be repeated every 2-3 years. Choose from this list of licensed local arborists.

Are there alternatives to treatment?

Untreated trees are at risk for a fatal EAB infestation. Removing and replacing ash trees is another option and can sometimes be the best choice. Dead or alive, ash trees can be safely removed by a licensed and insured arborist or tree service company.

What is the city of Aurora doing to prevent the spread of the EAB?

Aurora’s Forestry Division has inspected all city ash trees and will be treating or removing them. As of yet, the EAB has not been detected in the city of Aurora.

Is it ok to plant new ash trees?

NO, it is prohibited to plant ash trees in Aurora because of the EAB threat. Find other trees recommended for planting in Colorado on the Recommended Trees for Aurora Guide.

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