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Help prevent the spread of emerald ash borer in Colorado

October 4, 2013

The insect poses a serious threat to Colorado's urban forests -- including those in Fort Collins, where ash species comprise an estimated 15-20 percent of all trees.

Tree damage caused by the emerald ash borer.In late September, the Colorado Department of Agriculture announced that emerald ash borer, an invasive insect responsible for the death or decline of tens of millions of ash trees in 21 states, was detected in Colorado for the first time. The insect poses a serious threat to Colorado’s urban forests -- including those in Fort Collins, where ash species comprise an estimated 15-20 percent of all trees. The Denver metro area alone has an estimated 1.45 million ash trees.

The emerald ash borer is a small, metallic-green beetle first detected in North America in 2002. For five years, the CDA has been conducting early emerald ash borer detection activities in Colorado through the Cooperative Agricultural Pest Survey program, in coordination with the USDA Animal and Plant Health Inspection Service, Colorado State Forest Service and city foresters.

Confirmed Sept. 23 in Boulder County

Specimens collected on Sept. 23 from an ash tree in Boulder County were confirmed by the USDA to have emerald ash borer. Colorado is now the western-most state with confirmed presence of the borer, and one of four states reporting detection for the first time this year.

The CDA, CSFS and other partners have assembled an incident command team and are following a response plan, which involves taking steps to define and quarantine a regulated area, expand detection efforts and increase education and outreach. CSFS Community Forestry Program Manager Keith Wood said the public has an important role to play in minimizing the spread and impacts of the insect.

“Most important is that you should never transport firewood or other untreated products from ash trees, as this is the most likely method of accidental spread,” Wood said. “Transporting firewood of various tree species is the primary cause of many costly insect introductions.”\

Signs of infestation

Wood says property owners also should be on the lookout for signs of ash tree infestation, which include thinning of upper branches and twigs, loss of leaves, serpentine tunnels under the bark, vertical bark splitting or increased woodpecker activity. Any suspect trees should be reported to the CDA.

Homeowners also have the option to apply chemical treatments annually to help protect high-value trees, but the team discourages doing so unless they are within 15 miles of a positive detection. Currently, the only positive in-state identification was found in the City of Boulder.

“We don’t want people unnecessarily using insecticide treatments that aren’t warranted at this time,” Wood said. “They can be very expensive, and if applied incorrectly can be a detriment to the environment.”

He says foresters are hopeful that emerald ash borer will be less successful here than it has been in the Midwest, because Colorado lacks large, unbroken stands of native ash and has only sporadic planted trees in urban settings.

Landowners with any suspect ash trees should contact the CDA at 888-248-5535 or email More information about insects and diseases that threaten Colorado trees is available at the CSFS website.

Contact: Ryan Lockwood
Phone: 491-8970