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The Emerald Ash Borer Has Arrived In Broomfield. Here's What That Means

Will Parson/Chesapeake Bay Program
CC BY-NC 2.0
An adult emerald ash borer is seen in captivity at the University of Maryland in College Park, Maryland.

It was the call Tom Wells had been dreading for years.

Earlier this summer, a Broomfield resident discovered a small, dead bug lying on the sidewalk outside of their home. They scooped the carcass up in an envelope and brought it to Wells, the city and county forester, at the public works department.

Wells, suspecting it was the notorious pest that had been killing Colorado trees since 2013, first took the beetle body to the Colorado Department of Agriculture. The department then forwarded it to a lab at Colorado State University, which shipped it off to a federal lab in Michigan.

Several weeks later, Wells got his answer.

“They all confirmed that it was the emerald ash borer,” he said. “I always felt that it was somewhere in Broomfield for a while. I was just confirming what I believed.”

The discovery of the borer in the Denver suburb this summer represents the first time one of the beetles has been found outside of a federal quarantine in Boulder County. In a statement on Tuesday announcing its discovery, beetle experts said residents should take caution.

“The primary purpose of this quarantine has been to slow the spread of (the borer) in Colorado, and we believe this is one reason it’s taken so long for the pest to be confirmed outside Boulder County,” said Laura Pottorff, a plant health and certification chief with the state’s Department of Agriculture.

“Based on recent data from the eastern U.S., our expectation is that (the borer) cannot be prevented from leaving the quarantine,” Pottorff added. “We’re just glad we’ve given Front Range communities more time to better plan and prepare for its arrival.”

The emerald ash borer is native to Asia and arrived in North America during the 1990’s, according to the Colorado State Forest Service. The beetle was first confirmed in Colorado in Boulder in 2013.

Since then, the insect has made itself at home along the Front Range. By the end of 2015, the entire city of Boulder was considered infested. In 2017, the bug was found in Lafayette. The next year, it was spotted in Lyons.

Across the country, the insect has killed millions of ash trees in at least 35 states, according to the Forest Service.

Tom Wells said the city and county of Broomfield had already been preparing for the borer’s arrival due to the bug’s tendency to travel. Its most common method of transportation is with the help of humans moving infested firewood, logs, branches, wood chips or other ash wood, he said.

In anticipation of its arrival, Wells’ staff has removed 1,500 ash trees from public land and treated an additional 931 trees with pesticides in the past three years.

“The thing about emerald ash borer is if you don’t do anything you’re gonna have a whole bunch of trees die at once,” he said.

Once the beetles burrow into an ash tree, the plant typically dies within two to four years. There is no cure once it’s infested, Wells said.

“This is the first time in my 30 years of working in urban forestry that I have done a preventative spray program,” he said.

Wells said if residents aren’t sure if they have an ash tree on their property, they should contact a professional arborist.

“If it’s a tree that you want to keep and it's worth saving, then you should go ahead and arrange for them to set up a treatment program because the pesticide we use needs to be applied by a licensed pesticide applicator,” he said. “If you don't want the tree anymore, go ahead and proactively remove that tree while it's alive and replace it with a more suitable species.”

In a statement, the Colorado Emerald Ash Borer Response Team included the following tips:

  • Determine now if you have any ash trees. Identifying features of ash trees include compound leaves with five to nine 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 online.
  • 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 online. 
  • Beware of imposters. Other insects like lilac/ash borer, ash bark beetle and flat-headed apple tree borer may look like the emerald ash borer or cause similar tree symptoms. For more information, go here.
  • 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 quarantine, allowing for significant fines for those who move untreated wood from the area.
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