Emerald ash borer, a tree-eating insect, found in Arapahoe County

BY TAYLER SHAW TSHAW@COLORADOCOMMUNITYMEDIA.COM

A threat to ash trees has come to the south metro area as Arapahoe County has identi ed its rst case of emerald ash borer, an invasive insect that eats and kills North American species of ash trees. e insect was detected in a small area in northeast Littleton, the county announced June 29 in a news release. Arapahoe County agencies, Colorado State University Extension specialists and experts from surrounding municipalities con rmed it is emerald ash borer.

“EAB (Emerald ash borer) is the most destructive insect pest in trees that we have ever seen in North America,” Lisa Mason, a horticulture specialist and entomologist at Colorado State University Extension O ce in Arapahoe County, said in the release.

Now, the county and surrounding local municipalities are recommending residents who have an ash tree make a plan of action.

“Homeowners and HOAs (homeowners associations) with ash trees will eventually have a signi cant nancial decision to make whether they choose to treat their ash trees with insecticides or remove them,”

Mason said in the release.

What is this insect?

Emerald ash borer beetles were rst discovered in Colorado in 2013 within Boulder County, according to the release.

“Since then, the destructive wood-boring beetles have been found in Broom eld, Larimer, Erie and ornton,” the county said in the release. “ e town of Carbondale also recently reported a con rmed case discovered on June 16.”

Sam Waggener, Lone Tree’s code enforcement coordinator and city forester, warned of the spread of the insect during the city’s Arbor Day celebration in April.

“Emerald ash borer is an insect that a ects only ash trees and has not made it to the south metro area, but in due time, it will,” Waggener said during the event.

According to Lone Tree’s website, the metro Denver area has approximately 1.45 million ash trees.

In Lone Tree alone, there are an estimated 5,400 ash trees. Over in Littleton, there are an estimated 45,000 ash trees. Englewood estimated it has 20,000 ash trees.

On average, 15% of urban trees are ash trees, Arapahoe County said in its release.

What now?

If a resident has ash trees on their property or within their homeowners association community, they will be impacted at some point, according to the county.

“Eventually, all ash trees will need to be treated for EAB (emerald ash borer) with insecticides, or the trees will need to be removed,” the county said on its website. “You have a decision to make as to whether you remove or treat your ash tree.”

Insecticide treatments depend on the size and health of each tree, per the news release.

Mason said one study showed healthy ash trees can be treated with “emamectin benzoate” successfully after an infestation by emerald ash borer, as long as the tree has not lost more than approximately 30% of the canopy.

To detect emerald ash borer, Mason recommended residents look for distinctive D-shaped exit holes, bark splits and S-shaped tunnels underneath the bark.

Other signs include gradual tree canopy thinning and dieback, as well as abnormal shoots of growth, smaller-than-normal leaves and heaving woodpecker activity, Mason added.

In the release, the county said that since emerald ash borer kills trees over a period of several years, trees that are not candidates for insecticide treatments will eventually need to be removed.

Arapahoe County municipalities are currently prioritizing ash tree insecticide treatment and removal, according to the release. e county has a webpage with resources available at bit.ly/arapash.

Surrounding local municipalities also have webpages containing information and resources for residents to learn more about emerald ash borer and what they should do. ey are listed below:

Littleton: bit.ly/littletonash Englewood: bit.ly/englewoodash Cherry Hills Village: bit.ly/cherryhillsash Greenwood Village: bit.ly/ greenwoodash Lone Tree: bit.ly/ lonetreeash

Arapahoe County said residents who have questions about emerald ash borer and who want more information about a possible diagnosis and treatment options should contact the Arapahoe County CSU Extension O ce at MasterGardener@arapahoegov.com or (303) 7301920. For those living in Douglas County, the Douglas County CSU Extension O ce contact information is listed at douglas.extension. colostate.edu.