The Emerald Ash Borer (EAB) is a very serious and destructive pest of ash trees. State officials have confirmed the presence of EAB in the City of Arvada in 2020. First detected in Boulder, Colorado in 2013 and more recently found in neighboring municipalities, this invasive and highly destructive insect attacks and kills ash trees. The City of Lakewood continually monitors for EAB and confirmed presence in Lakewood in September of 2024.
View Confirmed Presence Map
The adult insects are present from May to October. The EAB larvae feed under the bark of ash trees, eventually girdling the tree and cutting off nutrients. These trees typically die within 2-4 years of first symptoms.
Helpful resources can be found on the Colorado State Forest Service EAB webpage and with tree identification information, area insect detection reports, and more. Visit this page for updates and resources.
What to do about this pest
Visit the Colorado State Forest Service EAB website for further details and directions.
How to Spot Tree Symptoms
Determine if you have any ash trees on your property.
True ash trees have compound leaves with 5-9 leaflets, and buds, leaflets and branches grow directly opposite from one another. Mature trees have diamond shaped bark ridges.
Use free resources to assist in identification.
The Colorado State Forest Service and Colorado State University Extension have developed EAB/Ash Tree ID App for both Apple and Android devices. Simply search the app store for “ash tree.”
Watch for symptoms.
Symptoms can include branch dieback near the top, D-shaped exit holes 1/8-inch wide, serpentine tunnels under the bark and new sprouts on the trunk and branches. Watch the video above to learn how to identify symptoms.
Evaluate whether chemically treating a tree is worthwhile.
Large, high-value healthy trees might warrant early treatment as “insurance” much more than young, unhealthy or poorly located trees. If you hire someone to apply pesticide treatments to protect ash trees, make sure the applicator is licensed by the Colorado Department of Agriculture as a commercial pesticide applicator.
Consider removing or replacing ash trees.
You may opt to remove or replace ash trees before the pest’s arrival and instead plant diverse new tree species. This can offer more long-term benefit than paying for preemptive chemical treatment in areas where the insect has not yet been detected.
Hire a Tree Contractor
Understand treatment options.
Treatments exist that are capable of helping infested trees recover if applied early in an infestation.
Avoid Transportation
Never transport firewood or other products from ash trees as this is the most likely method of accidentally spreading the pest.