This is the Emerald Ash Borer. Agrilus planipennis Fairmaire. Native to Asia, these "jewel borers" (Buprestidae) were first described in western literature in 1888 by Léon Fairmaire from a harvested specimen sent to him by the priest Armand David. It was described a second time and named agrilus marcopoli by Jan Obenberger in the 1930's because Fairmaire's description was unknown to Obenberger at the time. This scarcity of information would be typical of the bug until it was recognized in Canton, Michigan in 2002.

Since then Emerald Ash Borers have managed to spread fairly prodigiously throughout North America, affecting trees on the East coast as far north as Maine, as far south as Georgia, and heavily through the midwest to Nebraska, Missouri, Iowa, Minnesota, Eastern South Dakota, and a few satellite populations cropping up in Louisiana, Arkansas, Oregon, Texas and right here in Colorado.

A highly invasive species, certain efforts to contain the spread of Emerald Ash Borer have been abandoned for lack of effectiveness. Surveys and studies lead to a presumed complete mortality of Ash trees within 10 years after introduction to the area.

Emerald Ash Borers were confirmed to be in Boulder, Colorado in 2013. Since then they have spread throughout the Denver Metro Area and most recently have been confirmed in Littleton, Lakewood and Centennial in 2024.

What does the Emerald Ash Borer look like?

Emerald Ash Borers are actually fairly easy to identify. While there are plenty of insects that appear similar in color, size and shape make them rather unique. First and foremost is the combination of colors:

That red-colored abdomen is the easiest way to tell, combined with their size. Take out your phone:

If it's big enough to cover up your charging port, it's big enough to be an EAB. Combine that with the color and red abdomen, you can be fairly certain. Even variations that have been found of EAB that vary in color from copper to cyan, the abdomen coloration is the telltale sign.

There are other bugs that look fairly similar in Colorado, but can be easily identified by shape, color, or telltale ridges:

Agrilus anxius, or the Bronze Birch Borer, doesn't have a red abdomen and has ridges on its pronotum:

Its coloration is also usually indicative of its namesake, "Bronze."

Agrilus Liragus, or the Bronze Poplar Borer, is likewise easily distinguished due to its color and the ridges on the pronotum:

Agrilus vittaticollis, or the Hawthorn Root Borer, easily distinguished by the coloring of the stripes along the pronotum and abdomen.

Ctenicera resplendens, a "click" beetle. Notice the ridges on the wing.

Temnoschiela chlorodia, or the Green Bark Beetle. Completely different shape with a pronounced segmentation between the thorax and the abdomen.

All other insects in the state of Colorado that might be mistaken for Emerald Ash Borer can be easily differentiated by the fact that they're not big enough to cover the charging port on your phone or the wildly different shape.

How Do I Know If My Tree Is Infected?

The most obvious sign is that Ash tree is dead, unfortunately. If you've spotted holes like these in your tree it is most likely too late to save the tree. Because underneath these holes are the larval galleries:

This kind of damage to the phloem of the tree prevents it from being able to transport water and nutrients from the roots to the leaves, effectively girdling the tree and killing everything above the roots. If your Ash tree shed a lot more seeds last year, that is an alarming sign that the trunk has effectively been girdled and those seeds were an emergency measure to propagate the tree. Keep an eye out in your neighborhood and if you see any Ash trees that aren't looking healthy, it's probably already in your area. Other animals will give you signs too.

These little birds are another sign that a tree may be infested. If you're noticing that your Ash tree has woodpeckers around it during the spring, chances are they're hunting these guys just below the bark:

The good news is that if woodpeckers are still incessantly interrupting conversations with their drumming on your Ash tree, it's very possible you can still save the tree.

How Can I Save My Tree?

With over 8 Billion Ash trees in North America, efforts to curtail the spread of Emerald Ash Borer have been numerous and unfortunately unsuccessful. While already being designated as Threatened by the IUCN in 2017, it is still listed as Apparently Secure by NatureServe due to the success of various treatments and management by various states. It may be critically imperilled in the wild, but in our neighborhoods and parks they can be easily protected thanks to the discovery of several systemic treatments.

Systemic treatments (specifically Emamectin Benzoate) are the best method for preventing EAB infestation. The chemical proliferates throughout the tree by direct application to the phloem, the part of the tree mentioned earlier that is responsible for transporting water and nutrients throughout the tree, and the part of the tree that the insects prefer to eat. A systemic injection is capable of killing EAB larvae that are already in the tree, and quite quickly. One treatment can also protect a tree for 2 years, but this requires specialized equipment and adherence to the instructions for the chemical involved. Because it is quite expensive, many services don't use the required amount of chemical, and this results in either a shortened period of protection or no protection at all. At ~$475/quart, you want to be sure that the company performing the service isn't pinching pennies when it comes to deciding the dose for your tree.

If you want to protect your tree and in 10 years time have a unique tree to your area, give the professionals at Arbor Pro Tree Experts a call.