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Colorado State Forest Service News

Emerald Ash Borer Detected in Lafayette

A tree in Lafayette, Colo. damaged by the emerald ash borer.
A tree in Lafayette, Colo. damaged by the emerald ash borer.

LAFAYETTE, Colo. — This week, the invasive tree pest emerald ash borer (EAB) was confirmed in the City of Lafayette. This detection is still within a quarantine area established to try and prevent the human-assisted spread of EAB, but represents only the third confirmation of EAB anywhere in Colorado outside the City of Boulder, where the pest was first detected in 2013. EAB has also been confirmed in Gunbarrel and Longmont.

An estimated 15 percent or more of all urban and community trees in Colorado are ash species susceptible to being killed by EAB – and a majority of these trees are on private land.

Last Thursday, a Boulder County forester identified an ash tree on private land in the vicinity of Arapahoe Road and North 95th Street as potentially infested with EAB. He immediately notified partners on the interagency Colorado EAB Response Team, which is working to manage the spread and impacts of the pest in Colorado. An insect specimen found in the tree was provided to the Colorado Department of Agriculture and then to Colorado State University for confirmation, and the suspect tree also was visited by experts from the CDA and Colorado State Forest Service, at which time an additional tree on an adjacent property was identified as likely being infested with EAB. Yesterday, the insect specimen was confirmed by experts with CSU as being emerald ash borer.

It is unknown whether EAB arrived in Lafayette by natural spread or via accidental human transport, such as in firewood or other raw ash material. The pest had previously been confirmed in Gunbarrel, just to the north, and populations of the insect are capable of spreading a half-mile each year on their own.

The emerald ash borer can reduce an ash tree's foliage, as shown on this tree in Lafayette, Colol
The emerald ash borer can reduce an ash tree’s foliage, as shown on this tree in Lafayette, Colo.

EAB was first confirmed in Colorado in September 2013, in the City of Boulder. In November 2013, the CDA established a quarantine zone around Boulder County in an effort to protect Colorado ash trees. At this time, EAB has not been detected in Colorado outside of Boulder County or the EAB Quarantine area. However, the CSFS and other members of the EAB Response Team continue to try and detect the pest in new locations.

“Having a new detection in this area was not unexpected, but certainly highlights the need for Front Range communities to be planning now, before EAB arrives,” said Keith Wood, CSFS community forestry program manager.

Many Front Range communities already have EAB management plans in place, including Lafayette. In response to the 2013 identification of EAB in Boulder, the Lafayette Parks Department created an Emerald Ash Borer Response Plan and began an inventory and assessment of all ash trees on City-owned land including parks, streetscapes, cemeteries, city facilities and the golf course. Unhealthy trees graded at the lowest assessment level are in the process of being removed and replaced with new species.

The City is estimated to have approximately 22,000 ash trees; those on City-owned lands comprise only about 3 percent of the overall ash population, with the majority of the trees being on private land.
The City will not be treating private ash trees and recommends that residents take action now to assess and evaluate treatment for their trees.

The EAB Response Team remains committed to EAB outreach and detection efforts in Boulder County and surrounding areas, in addition to enforcing the quarantine. Over the past three years the CSFS, partnering with Boulder County and the City of Boulder, has set hundreds of traps targeting EAB to try and detect its presence along roadways within Boulder County. However, the pest is extremely difficult to detect when its numbers are low in the area.

EAB tips for Boulder County 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. 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 CDA 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 winding S-shaped tunnels underneath. 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 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, go or

The emerald ash borer (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 then it has spread to 30 states, including Colorado. As a non-native insect, EAB lacks predators to keep it in check. EAB only attacks ash trees in the genus Fraxinus, but has also been documented infesting white fringe tree. Mountain ash and other tree species are not susceptible.

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

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