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Colorado State Forest Service News

Emerald Ash Borer Detection Efforts Continue Over Winter

Branch sampling reveals an overwintering EAB larva that would have emerged as an adult insect in the spring.

BROOMFIELD, Colo. – Although the tree-killing emerald ash borer (EAB) remains dormant over the winter months, the interagency team working to manage the pest in Colorado is not.

The Colorado EAB Response Team – comprised of the Colorado Department of Agriculture, USDA Animal and Plant Health Inspection Service, Colorado State Forest Service, Colorado State University Extension and other partners – is assisting Front Range communities in their efforts to detect the presence of EAB.

Branch sampling and peeling “trap trees” help seek out the overwintering larval stages of EAB before they emerge as adult insects in the spring. Trap trees are ash with bark rings previously removed to intentionally stress the trees and make them more desirable to EAB adults seeking new hosts.

“Emerald ash borer is a notoriously difficult pest to find, particularly during the early stages of an infestation,” said Micaela Truslove, EAB program coordinator, Colorado Department of Agriculture.

“Branch samples and trap trees are mechanisms that can help us detect this destructive pest as early as possible.”

Systematic sampling for EAB in Colorado’s ash trees began in Boulder in the fall of 2013. Since then, many other communities have completed some form of branch sampling, including Arvada, Aurora, Centennial, Denver, Greeley, Littleton, Lone Tree, Longmont and Sheridan. Boulder County soon will be peeling trap trees it established earlier in 2014.

Recently, the EAB Response Team has assisted Berthoud, Lafayette, Longmont and Milliken with branch sampling and/or trap tree-peeling efforts. In January, the team will assist Federal Heights with additional branch sampling. The team also is hosting EAB identification workshops at the City of Boulder Forestry facilities through January, targeting green industry and landscaping professionals.

To date, EAB has not been detected in Colorado outside the City of Boulder. Truslove says the results of any EAB sampling activities that confirm a positive detection outside the city will be made available to the public, and that sampling efforts are ongoing.

“There is the potential for new detections at any time of the year. Communities are out looking, and will continue looking, until EAB is found,” she said.

A non-native pest responsible for the death of millions of ash trees and billions of dollars in costs in 24 states, EAB was first confirmed in Boulder in September 2013. The pest attacks and kills all true ash species, which comprise an estimated 15-20 percent of all trees in the state’s urban and community forests.

What Coloradans Need to Know About Emerald Ash Borer

  • Learn how to identify ash trees, and signs of EAB infestation in ash trees: thinning of leaves and upper branches and twigs
    • serpentine tunnels produced by larvae under the bark
    • D-shaped exit holes 1/8-inch wide
    • new sprouts on the lower trunk or lower branches
    • vertical splits in the bark
    • increased woodpecker activity
  • Don’t apply unnecessary chemical treatments, and talk to a professional forester or arborist before applying any treatment. If hiring someone to apply pesticide treatments, the applicator must be licensed by the Colorado Department of Agriculture as a Commercial Pesticide Applicator. Chemical treatments are not recommended more than 5 miles from a positive detection.
  • Never transport firewood or other products from ash trees, as this is the most likely method of accidental spread. A quarantine is now in place in Boulder County and surrounding areas to try and prevent the human-assisted spread of EAB.

For current information about EAB in Colorado, including the current quarantine in Boulder County and surrounding areas, go to If you think you have EAB in your ash trees, please contact the Colorado Department of Agriculture at (888) 248-5535 or email

The Colorado EAB Response Team is comprised of members from the following agencies/organizations: Boulder County, City of Boulder, Colorado Department of Agriculture, Colorado State Forest Service, Colorado State University Extension, Colorado Tree Coalition, Green Industries of Colorado, University of Colorado and USDA Animal and Plant Health Inspection Service.