Watch for This “Green Menace” Killing Trees Across Colorado

Colorado Bug Alert: What Invasive Insect Is Threatening Local Trees?

Summer time is a prime time for many bugs and insects to make themselves known here in Colorado.

The Centennial State just wrapped up tick season, and now there's ANOTHER creature to worry about. This one won't bite you or try to drink your blood, but it could kill thousands of trees throughout the state.

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What Is the Emerald Ash Borer and Why Should Colorado Be Worried?

In a recent report from Rocky Mountain PBS, something called the emerald ash borer has been spotted in Colorado.

This invasive wood-boring beetle is native to eastern Asia, but was found on June 17, 2025 in Denver.

When Was the Emerald Ash Borer First Found in Colorado?

It was initially spotted back in 2013 in Boulder, according to Colorado State Forest Service.

Over the years, it's been spotted in Northern Colorado.

READ MORE: This Gross And Invasive Insect Has Returned to Northern Colorado

Why the Emerald Ash Borer Is Considered the Most Destructive Tree Pest in North America

Described as a "green menace" the emerald ash borer has killed millions of ash trees in the central and northeastern United States and Canada. It is now considered the "most destructive tree insect pest" on the continent.

How the Emerald Ash Borer Kills Trees

This pest has no natural predators in the United States, which allows it to spread rapidly.

The creature's larvae feeds on vascular tissue which completely messes with nutrient and water flow to the tree thus killing it, according to experts.

Why Colorado’s Urban Forests Are at Risk

Having a creature that can destroy ash trees is devastating for Colorado's natural ecosystem. At least fifteen percent of all urban and community trees in the Centennial State are ash, according to the Colorado State Forest Service.

How to Tell If Your Ash Tree Has an Emerald Ash Borer Infestation

If you have ash trees on your property, there are a few things to look out for that could point to an emerald ash borer infestation.

• Thin or sparse leaves/ branches in the upper part of the tree
• Vertical splits in bark
• More woodpeckers than normal
• Mini leaves located at the tips of branches (specifically during late summer)

Who to Contact for Emerald Ash Borer Problems in Colorado

If you or someone you know is dealing with an infestation like this or wants more information about the creatures, you are encouraged to contact the following people:

Carrie Tomlinson: CSFS Urban & Community Forestry Manager

Dan West: CSFS Entomologist

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