Emerald Ash Borer in Denver, CO

Trees keep neighborhoods beautiful and provide housing for beneficial wildlife. More recently, they've been under threat of far less beneficial wildlife.

The emerald ash borer is an Asian insect that migrated to the US sometime in 2002. Since then they've been a consistent threat to all true sash trees, wiping out millions of acres in Michigan and Montana. 

Since their discovery in Colorado in 2013, experts have been keen to track and stop the spread of borers. 

The following explains how to spot this insect as well as steps to take to limit damage and protect trees. 

Spotting Emerald Ash Borer Damage

A tree infected starts to deteriorate at the top with a descending pattern of damage. An ash tree with declining health deserves attention anyway, but spotting and stopping borers is paramount to curtail their spread. 

When inspecting the bark of a tree a tale-tell sign of borers is D-shaped holes and galleries in. 

The battles don't bore too deep, so an increase in woodpeckers and beetle eaters is another symptom.

If you spot damage and deterioration in a tree, contacting an arborist is ideal to protect your tree and your neighbors as well. 


You're unlikely to see the beetle itself. They live in the higher branches and crown of the tree and aren't particularly large.

They are characterized mostly by their shiny green, nearly metallic color. They average about 2 cm in length with large black eyes and a flat back. Though they have three segments the head and thorax blend together and the long abdomen is the most visually striking with treen on top and a purple color under the wings. 


As the name suggests the emerald ash borer feeds on ash trees. This includes all species of true ash including white, black, green, and blue ash. 

Wild ash in Colorado are a form of pseudo-ash that doesn't attract the bugs. This leaves private, urban ash as the most likely target of the species.

As they can only fly a short distance and live generations in a single tree, they mostly spread through high altitude winds and transportation by humans. A single infected ash endangers any neighboring trees making early detection key. 

Invasive Species Dangers

An invasive species is distinct from a predatory species. While it could be argued that nature is in a fight for survival and intervention is an academic matter, with invasive species the line gets erased.

Trees, like other living things, develop defenses against common predators in their environment. No defense is impregnable, but the general arms race leads to an equilibrium. With an invasive species, the trees have no natural defenses and therefore die en-masse.

Steps to Take

If you suspect a tree is suffering from an emerald ash borer infection, reach out to knowledgeable arborists. Don't wait for signs of damage, ash trees can be protected with chemical treatments in the bark and soli to deter insects.

Contact us to diagnose your trees and provide prophylactic and active care. Together we can limit the harm of these pests and keep our trees beautiful. 

Posted on in Tree Removal.