Emerald Ash Borer

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beetle-eabThe Emerald Ash Borer (EAB) is a non-native, wood-boring beetle that can attach to all ash tree species. This insect was first discovered in Michigan in 2002, and since then it has spread to 22 states, including Colorado. The ash tree is a very commonly planted tree in many communities. EAB has killed tens of millions of ash trees in the United States. Once the EAB population builds in numbers, ash mortality is near 100%.

On June 6, 2016, the first siting of the EAB was reported in Longmont.  Longmont is estimated to have an ash tree population of approximately 43,000 trees and the City is now working to protect 900 of the approximately 2,800 City--owned Ash trees in Longmont.  

The City of Boulder first discovered and confirmed the presence of EAB in September 2013. Boulder Urban Forestry delimitation survey determined EAB has spread within the City of Boulder.

On Nov. 12, 2013 the Colorado Department of Agriculture established a quarantine zone around Boulder County, the City of Erie, and the Republic Landfill (north Jefferson County) off of Highway 93.

The City will be gathering data using an Unmanned Aircraft System (UAS) to help determine the spread of EAB in Longmont.  The UAS (drone) will fly over the tree canopy of several public parks including Valley Park, Hover Park, Pratt Park, Loomiller Park, Willow Farm Park, and also Twin Peaks Golf Course.  The City will provide web notifications to the public concerning all approved missions of where and when UAS are authorized to operate.Emerald_ash_borer_on_penny

Top Five EAB tips for Longmont and Front Range Residents

  • 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.
  • If you have an ash tree, start planning. Decide if the overall health of the tree merits 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 CDA as a Commercial Pesticide Applicator. 
  • Recognize signs of EAB infestation. Property owners with ash trees should be on the lookout for thinning of upper branches and twigs, loss of leaves, D-shaped 1/8-inch holes on the bark, vertical bark splitting or increased woodpecker activity. Report suspect trees by calling the Colorado Department of Agriculture at 1-888-248-5535 or filling out their 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. For more information, visit
  • 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 are under a federal EAB quarantine, allowing for stiff fines for those who move untreated wood from the area.

Additional Resources


Picture of bark removed on an EAB infected ash tree, exposing galleries caused by the EAB larva.

Video Library:

Listen as City Forester, Ken Wicklund, talks about the discovery of EAB in Longmont and how residents should begin preparing.


Enjoy this fun and educational video put together by the Denver Botanic Gardens to spread the word about EAB in Colorado.

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