Emerald Ash Borer in Colorado: Identification, Treatment & Removal

Emerald Ash Borer Is Spreading Across the Front Range

Emerald ash borer (Agrilus planipennis) is an invasive wood-boring beetle first confirmed in Colorado in Boulder in 2013. It has since been detected in communities across the Front Range, and green and white ash — among the most commonly planted shade trees in Colorado — are squarely in its path.

How to Identify EAB on Your Ash Tree

EAB larvae feed on the cambium just under the bark, cutting off the tree’s ability to move water and nutrients. Damage progresses top-down, so by the time the whole canopy thins, the infestation has usually been active for several years. Look for:

• D-shaped exit holes — about 1/8 inch wide, where adult beetles emerged.
• S-shaped galleries — winding tunnels under the bark, visible when bark is peeled away.
• Canopy dieback — thinning and dead branches starting in the upper third.
• Woodpecker damage — flecked, stripped bark as birds hunt larvae.
• Epicormic shoots — clusters of new sprouts low on the trunk as the tree stresses.

Why EAB Spreads More Slowly in Colorado

There is some good news: USDA Forest Service research shows EAB populations are expanding much more slowly here than in the eastern United States. Colorado’s ash trees are mostly urban plantings rather than continuous native forests, the drier climate is less favorable to the beetle, and proactive systemic-insecticide programs on the Front Range have reduced regional populations. That slower spread gives homeowners a real window to treat — or to plan removal on their own schedule.

Treatment vs. Removal: The Decision Framework

Tree condition	Recommended path
Healthy canopy, less than ~25% dieback	Systemic trunk-injection treatment every 1–2 years; keep monitoring
25–50% canopy loss, structural sound	Treatment may still work; get an on-site assessment
More than 50% decline or structural damage	Removal — declining ash become brittle and hazardous
Small ash (under ~15 inches) in poor condition	Removal and replacement is usually more cost-effective

Treatment is not a one-time fix — it is a 1–2 year cycle of systemic insecticide applications by a licensed professional. For many homeowners that still pencils out far better than removal plus stump grinding and replacement.

What We Do for Ash Trees

Creative Tree & Stump provides EAB assessments across the Front Range, systemic treatment through our tree-health program, and safe removal of declining ash — including crane work for large trees near homes and power lines. If your ash is on the fence between treat and remove, call us for a straight answer.