How to spot Dutch elm disease in Denver and why protecting the urban canopy is so vital

One of the most destructive tree diseases is back in Denver.

Dutch elm disease ravaged the urban canopy in the city in the 1970s but disappeared in 2011.

But just last month, the aggressive tree killer was discovered again in the city.

This is a prime spot for Dutch elm disease to run rampant because of the many American elm trees along the parkway.

Infected trees can wilt and die within just a few months.

Not only would that be noticeable, but it could prove problematic for neighborhoods like this that rely on the large shade trees.

"It's a fungal pathogen that can move through root grafts," said arborist Taylor Judd.

It's not easy to see, but these massive American elms are at risk of a deadly disease spread within their roots and by pesky bark beetles.

"And those pests basically trap those fungal spores on their legs and they'll feed on your elm, and that's how it really spreads," Judd said.

Now the city is forced to remove several elms along parkways.

"How does it come back? That's a good question. It's hard to say if it's remained in the soil, if we get an excessive amount of moisture, how did that revamp? That's really unknown; exactly why," Judd lamented.

Once a tree is infected, it can't be treated it has to be removed.

So how can you tell if your elm tree has the disease?

Judd says to look at the top leaves.

"It looks like early fall colors in early spring/summer, you usually see early fall color. That's an indicator," he said.

Judd says the disease can even spread to trees some 40 feet apart so it's important to act quickly to not only protect these elms but also the neighborhood as many homes don't have air conditioning.

"They're relying on their tree canopy to cool their house. Even if you have a swamp cooler, when it's in the 90s, having some trees helps out a lot," Judd said. "Some of these trees are historic; 80-plus-year-old American elms, and we'd hate to see them go."

If you suspect Dutch elm disease in your elm trees, your best bet is to call an arborist to be sure and determine how to move forward.