Emerald ash borer has made its way to Colorado

Tom Ziola examines one of several ash trees at Sherwood Park. The emerald ash borer that attacks the trees has appeared in Colorado, the parks supervisor for the Grand Junction Parks and Recreation Department said.



Yes, it’s true. Enemy No. 1 in the tree world is living here in Colorado. Officials confirmed that the emerald ash borer, the most destructive pest to enter our state in recent years, was found near Boulder at the end of September.

Colorado is the 22nd state to deal with this pernicious pest, according to the Colorado Department of Agriculture.

In just over a decade since the borer was discovered in Michigan, it has killed more than 50 million ash trees, according to the department. Like many invasive pests, the emerald ash borer is native to another part of the world, and is suspected to have hitchhiked to North America from Asia on wood products. Its larvae slowly kill trees by tunneling under the bark, causing the top branches to die off.

The price of tree death and minimizing the damage will “easily range into the billions of dollars” to municipalities, property owners, nurseries and industries that use ash tree wood for commercial products, according to the U.S. Department of Agriculture.

But experts say it’s too early to kiss your ash goodbye. They say it’s time to chill out, assess the situation and plan for the borer’s eventual arrival in other parts of the state.

First, it’s important for homeowners to know there’s no cause for alarm. “There’s no reason to get excited,” said Bob Hammon, Colorado State University entomologist and an extension agent. “We’ve got to keep our eyes open for it and once we get it here, we’ll deal with it.”

Officials agree it is only a matter of time before the borer spreads to other areas, but no one knows when that will be. To prepare, experts are deciding how to best treat for the pest when it arrives, and setting up aggressive monitoring systems to detect the pest as soon as it sets up shop. Apart from keeping ash trees healthy, there’s not much else anyone can do to prevent the pest from invading and eventually killing trees.

At the moment, tree professionals are assessing the situation. Tom Ziola, the city of Grand Junction’s parks supervisor who also oversees forestry, horticulture and the cemetery, said his staff is inventorying how many ash trees are located in rights-of-way and on city property.

“So far, roughly 30 percent of our species population is ash (trees),” he said. This amount does not include ash trees planted on private property, in homeowners’ yards. For many reasons, ash trees are popular to plant in Colorado – they grow fast and display gorgeous fall foliage. The Colorado Department of Agriculture estimates that ash trees compose 15 percent of urban trees in the state.

“A monoculture isn’t good for this very reason,” said Ziola, referring to the large amount of one species planted in one area. The city’s challenge will be to maintain a canopy with diverse tree species once the borer arrives, as well as try to deal with the pest in infected trees.

“We’re going to work closely with CSU and the state forest service to be sure we head off any problems because it is just a matter of time,” he said. “We are not going to be able to protect every tree.”

There’s little doubt that the borer’s arrival will be a game-changer for the urban landscape. “There’s some neighborhoods around here where there are 100 percent ash trees,” Hammon said.

“Its damage potential rivals, if not surpasses, previous invasive organisms such as the fungus that wiped out the American chestnut in the early 1900s and the fungus/beetle vector associated with Dutch elm disease,” said CSU entomologist Whitney Cranshaw, in an email to forestry professionals and entomologists this month.

Dealing with the impacts of the borer will involve specific treatments plans and a short window of time in which infected trees can be treated for the pest. At this point, local officials plan on setting traps to determine when the borer expands its territory. After that, the focus will be on figuring out the best times to treat trees and what methods to use.

In the weeks since the emerald ash borer’s presence was confirmed in Boulder, some Colorado residents are seeing aggressive marketing tactics being used by some companies to convince homeowners to apply preventative insecticides, which are unnecessary and expensive.

“There’s no reason whatsoever to be treating trees for emerald ash borers in Grand Junction because there’s a few of them in Boulder,” Hammon said.

One company, called “Organo-Lawn,” advertised a “minimum treatment plan” to protect ash trees that are not even located in the quarantine area near Boulder, including deep-root soil injections of insecticides this fall (at a minimum $75). Although the advertisement says the borer only attacks ash trees, it includes a treatment plan for applying an insecticide called Merit to shrubs and flowers. It also incites a sense of urgency with “HURRY! Call now! We have a very short window this fall to apply the soil injection called Merit!”

The truth is experts have not yet decided the best course of action to treat the areas confirmed to have the borer. Any sort of effort to prevent the borer’s spread is futile and a waste of money at this point.

In another email to forestry professionals and entomologists, Cranshaw called these predatory attempts by companies to scare homeowners into spending money on unnecessary treatments “unethical and harmful.”

His advice? “A few years from now, when you have to decide to treat your ash tree or remove it, you likely will need to hire a company to help you out,” he said. “There will be many good ones to choose from. But to make the choice a bit easier, remember the name of that company knocking on your door selling you a service in 2013 (or 2014, 2015 ...) that was unneeded and inappropriate. And then hire someone other than that company.”

Erin McIntyre is an advanced master gardener, writer and Grand Valley native. Please email her at .(JavaScript must be enabled to view this email address) with story ideas or feedback.


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