EAB Found in Denver: What You Need to Know to Protect Your Ash Trees

In mid-June, the City of Denver confirmed the presence of the emerald ash borer (EAB) — a wood-boring insect that poses a serious threat to our beloved ash trees. The EAB has already caused widespread devastation in 37 U.S. states and parts of Canada, and now it’s here. But with your help, we can protect Denver’s urban forest.

Why It Matters

Ash trees make up a big part of our green landscape. In fact, 1 in every 6 trees in Denver is an ash tree, and 1 in 10 trees on public land is an ash. These trees shade our neighborhoods, clean our air and enhance our parks. EAB attacks and kills ash trees, often within just a few years. If we don’t take action, Denver could lose hundreds of thousands of trees — and the shade, beauty and benefits they bring.

Denver launched the Be A Smart Ash campaign ten years ago to empower residents to protect their ash trees. Since then:

• 6,000 ash trees have been treated in parks and parkways
• More than 1,000 ash trees have been removed where needed
• About 1,500 new trees are planted every year, with more planned to grow our urban canopy

What You Can Do

Now we need you to take action! If you have an ash tree on your property or in the public right-of-way near your property, here is what you need to know and the steps to take:

1. Identify Your Trees: Early detection gives us the best chance to save a tree. To identify if you have ash trees on your property, look for compound leaves with five to nine leaflets, opposite branching and diamond-patterned bark. Check out photos and tips for identifying ash trees.
2. Inspect your Trees: Know the signs of EAB – look for D-shaped exit holes, falling bark, wavy lines under the bark or woodpecker activity (especially Northern Flickers).
3. Make an Action Plan: If you have an ash tree, find a licensed tree care professional to discuss your options for treatment or removal and replacement. Proper treatments are 95% effective when applied by professionals. If removal is necessary, consider replacing your ash tree with a Denver Office of the City Forester-approved species.
4. Spread the Word: Tell your friends and neighbors about EAB and what they should look for to help stop the spread of EAB.
5. Final Tip: Transporting firewood spreads EAB. Don’t do it! Keep wood local, and work with a licensed tree professional for any tree removal.

Trees are vital to our environment and quality of life, as well as our property values. While Denver has prepared for the arrival of EAB, we also need your help to slow its spread. Together, we can take action to preserve and grow our urban forest for generations to come.