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The CSU Extension office in Broomfield City & County provides assistance and programs for citizens in the areas of Horticulture: Yard & Garden

Assess Trees this Spring for Emerald Ash Borer

Adult Emerald Ash Borer on Leaf

With the spring season, trees are emerging from their winter dormancy period, and the Colorado Emerald Ash Borer Response Team is encouraging residents to check their trees for insects and other pests.

Read this news release for spring tree tips and information on the emerald ash borer, including the repeal of EAB quarantine laws in Colorado.


In August 2019, national and state experts confirmed the presence of emerald ash borer (an invasive and highly destructive tree pest) in the City and County of Broomfield. Here is a list of recommended steps and resources:

What steps should Broomfield residents take?

  • Determine if you have any ash trees. Features of ash trees include compound leaves with 5 to 9 leaflets; branches, buds, and leaflets growing directly opposite from one another; and diamond-shaped bark ridges on mature trees. Useful resources: ash tree identification guide, free identification app for mobile devices, Colorado State Forest Service’s ash tree identification video.
  • 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 these symptoms:
      • thinning of leaves in the upper tree canopy
      • 1/8-inch D-shaped holes on the bark
      • vertical bark splitting with winding S-shaped tunnels underneath
  • Be aware of EAB look-alikes. 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
  • Report suspect trees by calling the Colorado Department of Agriculture at 1-888-248-5535 or by filling out their online EAB Report Form.
  • 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 still under a federal EAB quarantine, allowing for significant fines for those who move untreated wood from the area.

Additional EAB Resources:

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