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Emerald Ash Borer Tips For Colorado Residents

Posted on 10/02/2019
Emerald Ash Borer

What To Do About Emerald Ash Borer

Emerald ash borer (EAB) is an invasive, highly destructive tree pest. Recently, this pest has been confirmed near the Town of Berthoud, Broomfied and Westminster in less than two months.  EAB has been present in Boulder County since 2013 and is currently under quarantine.  There are plans to repeal the current quarantine due to the recent spread of the pest and difficulty in controlling the future spread.

EAB is a non-native, wood-boring beetle that is responsible for the death or decline of tens of millions of ash trees in the United States and Canada. This insect was first discovered in Michigan in 2002, and since has spread to at least 33 states, including Colorado. As a non-native insect, EAB lacks predators in North America to keep it in check. 

EAB attacks and kills both stressed and healthy ash trees, and is so aggressive that trees typically die within two to four years after becoming infested if not treated with pest control measures.  EAB an spread naturally or with movement of firewood.

Here are some tips for Front Range Residents about how to deal with Emerald Ash Borer:

  • Determine now if you have any ash trees. Identifying features of ash trees include compound leaves with 5 to 9 leaflets; leaflets, buds and branches growing directly opposite from one another; and diamond-shaped bark ridges on mature trees. More information about a related app for mobile devices is available at
  • If you have an ash tree, start planning. Decide if the overall health of the tree merits current or future treatment or if it would be best to remove and replace it with a different species. If you aren’t sure, contact a certified arborist. If pesticide treatment is the preferred option, the applicator must be licensed by the Colorado Department of Agriculture as a Commercial Pesticide Applicator.
  • Recognize signs of EAB infestation. Property owners with ash trees should be on the lookout for thinning of leaves in the upper tree canopy, 1/8-inch D-shaped holes on the bark and vertical bark splitting with S-shaped tunnels underneath. Report suspect trees by calling the Colorado Department of Agriculture at 1-888-248-5535 or filling out the EAB Report Form at
  • Be aware of EAB imposters. Other insects like lilac/ash borer, ash bark beetle and flat-headed apple tree borer may look like EAB or cause similar tree symptoms. To view EAB look-a-like insects, download the EAB Look-A-Like Insects Chart.
  • Help prevent further spread of EAB. Do not transport ash or any hardwood firewood, or any other untreated ash wood products, to other locations. Boulder County and some surrounding areas currently remain under a federal EAB quarantine, allowing for significant fines for those who move untreated wood from the area.
For more information about ash tree identification, the symptoms of EAB and treatment options, visit the link