Colorado Springs is asking residents to be on the lookout for an invasive beetle species that has jumped down the Front Range and into local ash trees.

City officials said Wednesday that a confirmed emerald ash borer infestation had been found in Colorado Springs for the first time. City foresters were already implementing a response plan and asked the public and tree management companies to watch out as the insect spreads.

Lead City Forester Matthew Puckett said that one of the city foresters was responding to an issue in a neighborhood in northeast Colorado Springs in July when she spotted concerning signs on a dying ash tree. The biggest initial giveaway was the D-shaped holes left by ash borer larvae when they hatch out of the tree.

The city cut down the tree and sent samples of the larva still inside to the Colorado State Forest Service, which confirmed them as emerald ash borers.

“Right now it’s isolated, but it will move. That pest is here to stay,” Puckett said.

Originally from eastern Asia, the emerald ash borer is a small green beetle that has been an invasive presence in the United States for more than 20 years. The borer tunnels through the bark of ash trees to lay eggs, eventually killing the tree after a few years because it doesn’t have any natural resistance to the infestation.

The first confirmed ash borer sighting in Colorado was in Boulder in 2013. Over the next decade, the borer slowly expanded on the Front Range.

While the ash borer has so far not killed as many trees as the mountain pine beetle or Dutch elm disease, experts say the beetle poses an existential threat to one of the most common species of tree in Colorado.

“Ash were, many times, planted as a replacement for elms in the landscape because of Dutch elm disease,” said Carrie Tomlinson, Urban and Community Forest Manager for the Colorado State Forest Service. “Now we’re having to go through the same thing with the ash trees because we didn’t support a diversity of species to replace the elms.”

According to the State Forest Service, the ash borer had not been detected further south than Parker and Highlands Ranch until this summer, which meant its arrival in Colorado Springs — around 50 miles south — was a leap. Puckett and Tomlinson thought the beetle likely hid inside firewood that somebody brought back from the Denver area.

An inventory estimated that there are around city-owned 17,000 ash trees in Colorado Springs, making up around one in every six trees managed by the city. Puckett finalized an emerald ash borer management plan in 2025 to prepare for the potential arrival of the beetle. Details in the plan were built on a decade of previous monitoring of the ash borer, including a longtime ban on the city planting new ash trees.

“We’ve had a lot of time to prepare, a lot of time working with the State Forest Service and other city foresters to learn what was successful and what was not successful,” Puckett said.

The management plan outlines a combination of monitoring, pesticide treatments and tree replacements that will be done for the city-owned ash trees.

The plan estimates that it would cost the city around $719,000 to provide an initial pesticide treatment to all of the city-owned ash trees. That treatment would be more than the annual operating budget for Colorado Springs’ forestry division. Puckett said the treatment would also need to be repeated every three years to keep the trees protected.

The limited funding means that only some trees will be treated to prevent infection. City foresters will plant new species of trees next to ash as future replacements and work to quickly remove trees that have died.

As for ash trees on private property, Puckett said that residents should learn the initial signs of an infestation and call a licensed arborist to handle any treatments or removals. A list of certified arborists in Colorado Springs will be published on the city website in the near future.