Emerald ash borer requires homeowner action, but not panic

Insect found in Arapahoe County

BY SHEA VANCE SVANCE@COLORADOCOMMUNITYMEDIA.COM

With emerald ash borer—an invasive, tree-killing insect—now in Arapahoe County, experts are advising people with ash trees to take action sooner rather than later.

“ ere’s no need for people to panic because they’ve got a little bit of time, but they should start thinking about that now if they haven’t already,” said Lisa Mason, horticulturist and entomologist at the Colorado State University Extension o ce in Arapahoe County.

e species targets ash trees, which make up roughly 15 percent of the urban canopy — the surface area shaded by trees — in Arapahoe County.

An infestation in northeast Littleton was identi ed on June 20 by South Suburban Parks and Recreation District sta . According to South Suburban, the exact location was within the open space area next to the Big Dry Creek East Trailhead, near the Broadway and Littleton Boulevard intersection.

Mary Danser, the Littleton city forester, said once the emerald ash borer invades an ash tree, it is essentially an “immediate death sentence” for the tree.

“You see the decline, and that means it’s too late to save the tree,” Danser said. “ at’s the reason it’s a big deal, or a bigger deal than other pests, because of its e cacy in killing the trees.” e reason for the jump down to Littleton is likely the transport of rewood across the city, Mason said.

Emerald ash borer — or EAB — was found in Boulder in 2013, having been brought to Colorado from Michigan. Since then, it has mostly stayed north of Denver.

Mason advises that residents in and around northeast Littleton start treat- ment or removal now, but said that most of the county still has time.

“ ere’s a lot of great replacement tree options, and we’re happy to help people gure out the replacement trees that work well for them,” Mason said.

To treat or to remove?

Now that the pest has made its way south of Denver, it will eventually affect all ash trees in Arapahoe County, slowly spreading over the course of the coming years. Untreated ash trees will die.

“Anyone with an ash tree will eventually have to make a nancial decision, whether they treat the tree with insecticides, or whether they have the tree removed,” Mason said. “ ey don’t have to make that decision right away.” e cost of each option can vary depending on the tree and the business being consulted.

Removal can be pricey up-front, but treatment may cost more in the long run. Some options require treatments every three years, and others can be as often as twice a year. e removal of one or multiple trees from a property, however, can decrease the value of the property, and all these factors should be considered when deciding whether to treat or remove, Danser said.

Because of the increased di culty of removal after an infestation, it will cost homeowners less to remove their ash trees ahead of time rather than wait for EAB to reach their area, according to Mason.

If a resident opts to treat their ash trees, the best way to go about it is to hire a licensed arborist, according to Danser. She said some stores and nurseries sell certain chemicals that can work, but are diluted, making them less e ective. e highly e ective forms of treatment are only available through licensed applicators, who also know how to apply them correctly.

Although it is possible to treat a tree after it has been infested, according to Mason, that treatment must be hasty. e best way to save an ash tree from EAB is to treat it before the insect invades.

A resident may also opt to remove their ash tree, which is the better course of action for less healthy trees, Mason said.

“If a tree is not healthy, it is probably not a good candidate for treatments, because the insecticides are systemic, which means the root system needs to be able to uptake the insecticide and spread it throughout the tree,” Mason said. “An unhealthy ash tree just simply would not be able to do that.”

Homeowners may choose to remove their ash trees, even if they’re healthy, depending on the value to the homeowner and homeowners associations.

Although Danser recognizes the nancial di erences between the options, she highly advises against removing a tree that is healthy and in a sustainable location (not growing under a power line).

“I would only recommend removals for undesirable ash trees,” she said. “If your tree is healthy and you are able, chemical treating your ash is the best thing to do to save your own tree, contribute to the greater urban canopy in your neighborhood, and ght against the EAB.”

What’s the big deal?

Without treatment or removal, an a ected ash tree will die, increasing the risk of falling trees, which can be hazardous to personal safety and property.

“Dead trees in an urban homeowner setting can be a dangerous thing,” Mason said.

e impact on the urban canopy also poses a threat to the community bene ts currently provided by ash trees, according to the Arapahoe County website.

“Healthy ash trees play an essential role in urban tree canopy health; they slow down stormwater runo , provide much-needed shade and greenery, and help mitigate climate change by storing sequestered carbon,” the webpage reads.

Littleton’s action plan

Littleton has a plan prepared, which Danser put together last year “knowing that [EAB] was coming, not expecting for it to come this quickly,” she said. “We thought we had more time.” e city has chosen roughly one third of its healthiest ash trees to treat with insecticides, and is in the process of removing and replacing its least healthy trees. Danser said that it’s important to get ahead of tree removal and not wait until EAB invades, as the removal then becomes dangerous and complicated due to infested wood being “incredibly structurally unsound.”

As for ash trees on residential properties, Danser is in the process of applying for a grant which would allow Littleton to subsidize tree removal or treatment. A survey currently live on the Littleton forestry website is collecting resident responses to gauge the need for such a program.

Although EAB has not been detected by nearby cities, several localities near Littleton have made action plans in preparation for the pest’s arrival.

Surrounding areas

Like Littleton, Englewood completed an EAB management plan last year, and has been treating eligible trees and designating others for removal. Englewood already has a subsidy program in place for chemical treatment and removal, o ering to cover 25 percent—up to $500—of the cost to the homeowner.

Lone Tree has been planning for the arrival of EAB and will look to treat eligible ash trees that are in optimal health.

Only one percent of Parker’s urban canopy is composed of ash trees, so as of now, the town is not treating for EAB prevention and is not planning on preemptively removing trees, but is monitoring for issues.

SEE EMERALD ASH, P39