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Emerald Ash Borer Tips For Colorado Residents

Posted on 10/02/2019
Emerald Ash Borer

What To Do About Emerald Ash Borer

Assess Trees in Spring to Prepare for Emerald Ash Borer
Colorado Department of Agriculture Repeals EAB Quarantine


BROOMFIELD, Colo. – April 13, 2020 – With a new spring season, trees are emerging from their winter dormancy period across Colorado to bring life, color and vibrancy to our urban forests.

With Colorado Arbor Day taking place this Friday, April 17, and National Arbor Day celebrated April 24, partners with the Colorado Emerald Ash Borer Response Team are encouraging residents to do a spring checkup on their trees. Vince Urbina, urban and community forestry manager for the Colorado State Forest Service, recommends residents thoroughly water their trees, remove weeds and/or grass growing close to the trunk and refresh the mulch to a depth of 4 inches.

“These are all tree-centered activities you can do while staying home and practicing social distancing,” Urbina said. “What better way to celebrate Arbor Day than appreciating and caring for the trees we already have working for us. Keeping our community forest healthy helps create resiliency against tree-killing insects.”

Another activity people can do this spring, Urbina said, is assess their trees for insects and other pests, including the emerald ash borer.

Along with trees, EAB larvae are also completing their overwintering period. Under the bark of ash trees on the northern Front Range, larvae are transforming into adult beetles that will emerge in May and June to infest new trees. First detected in Colorado in 2013, in the City of Boulder, EAB has since spread to other cities and towns on the Front Range. With ash trees estimated to comprise 15 percent or more of all urban trees in the state, this non-native, invasive pest poses a serious threat to urban forests.

“If you have an ash tree, check it to see if it has the symptoms of an EAB infestation,” Urbina said. Symptoms of a tree infested with EAB include 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.

“If you live along the Front Range and have trees, you should be preparing for EAB,” Urbina said. “The first step is to determine if you have any ash on your property. If you are not sure if your tree is an ash, contact a certified arborist who can accurately identify the tree and help you set a plan for any ash you may have, such as removing and replacing it or treating it for EAB.”

Colorado residents, especially those living on the Front Range, are advised not to plant ash trees. The Colorado Tree Coalition offers tips on finding the right tree to plant at Colorado Tree Coalition. Some nurseries in Colorado are offering delivery options for residents who want to plant trees for Arbor Day. Residents can also support their local nurseries on Arbor Day by purchasing gift certificates.

EAB Quarantine Repealed

Last year, EAB was detected in Broomfield, Westminster and unincorporated Larimer County, near Berthoud. These detections were outside of a quarantine area encompassing primarily Boulder County, established to slow the spread of EAB via the movement of ash nursery stock, firewood and other wood that may contain the pest. With EAB discovered outside of Boulder County, the Colorado Department of Agriculture found it necessary to repeal all quarantine laws, effective Dec. 30, 2019.

“The quarantine was successful and gave communities time to prepare for EAB,” said Laura Pottorff, plant health and certification section chief with the CDA. “Adult emerald ash borers can fly up to a half-mile once they emerge, so it could not stop their natural spread or eradicate them.”

Pottorff said that lifting the quarantine provides municipalities and companies more options for disposing of ash wood and fosters its reuse and recycling. The CSFS is planning to host an ash wood utilization workshop later this year in Fort Collins as part of its Your Ash is on the Line project.

Here are some tips for Front Range Residents about how to deal with Emerald Ash Borer:

  • 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 Emerald Ash Boer: A Green Menace.
  • 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 you do plan to treat the tree, the CSFS offers recommendations for selecting a tree-care company.
  • Plant trees.  Replace ash trees in poor health with diverse species.  The CDA offers a database of registered nurseries and landscape contractors.
  • 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 S-shaped tunnels underneath. Report suspect trees by calling the Colorado Department of Agriculture at 1-888-248-5535 or filling out the EAB Report Form at Colorado Department of Agriculture.
  • 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. To view EAB look-a-like insects, download the EAB Look-A-Like Insects Chart.
  • 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 currently remain 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, visit the link Colorado State Forest Service.