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Fort Collins arborists warn homeowners of a growing issue with an invasive beetle

An open hand holding a small metallic green bug.
City of Fort Collins
A city of Boulder forester holds an adult emerald ash borer. The shiny, metallic invasive beetles disrupt water and food intake in trees and can eventually kill them.

The City of Fort Collins says a problem with an invasive species continues to grow. The city’s forestry division says emerald ash borer, a species of beetle, is destroying trees within city limits.

Foresters first detected emerald ash borer in Fort Collins in May of 2020, but this past summer they were able to easily spot dead and dying trees impacted by the bug as the problem has spread.

A slice of wood with a dark trail cut through it. At the end of the path is a small grub-like bug.
City of Fort Collins
Evidence of an emerald ash borer. The feeding larva leaves a trail from where it hatched, growing in size as it feeds under the tree's bark.

"Early in an infestation it takes a few years to kill a tree, but later on when the populations are high, the trees can die in one or two years," said Ralph Zentz, an assistant forester with the City of Fort Collins.

A man sitting in a green shirt holding a small dog.
Ralph Zentz
Fort Collins' Assistant Forester Ralph Zentz in the shade with his dog Pebbles. Zentz says the emerald ash borer threatens about 33 percent of the city's tree canopy

The invasive species first appeared in the U.S. in 2003. Fort Collins has made efforts since then to treat trees, in particular ash trees. That's where the insect lays its eggs. Once that happens, it’s too late for treatment and the tree needs to be removed as the beetle’s larva feeds under the tree’s bark. The end result is brittle trees that become a fall hazard.

The city has been treating about 700 trees on city land a year. Ash trees make up about 14% of those trees and 33% of the city’s entire tree canopy.

Zentz says the city needs homeowners’ help to protect ash trees.

"If you want to save your tree, you need to protect it, and the only real protection is chemical protection,” said Zentz.

Fort Collins is also trying to kill the invasive pest with parasitic wasps. In the meantime, the city shared a list of local arborists who are available to help homeowners protect their trees.

Alex Murphy is the digital producer for KUNC. He focuses on creative ways to tell stories that matter to people living across Colorado. In the past, he’s worked for NBC and CBS affiliates, and written for numerous outdoor publications including GearJunkie, Outside, Trail Runner, The Trek and more.
As the Newscast Editor and Producer, I provide listeners with news and information critical to our region.