First signs of Dutch elm disease detected in North Dakota

For decades, the American elm has been one of the country's most treasured species, a hearty deciduous tree lining streets, parks and backyards providing a shady canopy.   

The species was widely planted in communities throughout North Dakota because it grows quickly, has a long life and is tolerant of compacted soils.

“Elms are beautiful, well-shaped trees,” said Tom Claeys, team leader at the North Dakota Forest Service, based in Bismarck.

Because of its characteristics, the tree was widely planted throughout the state, and while it has thrived for many years, the introduction of Dutch elm disease -- a fungus that was first recorded in North Dakota in 1973 -- has made the tree vulnerable.

This year, City Forester Koduah Owusu, said the number of diseased trees has increased.

He said, within the last week, the city has cut down 10 trees that were flagged with the disease, but he believes that number could climb to more than 40 by the end of the summer.

Most of those will be cut down in the southwest part of the city, where many cases have been detected.

The disease is caused by two closely related species of fungi, which are transmitted by bark beetles -- which transport the disease -- or root grafts.

“American elm is the most common tree we have in Dickinson,” Owusu said. “The disease is spreading because there are so many of them planted close together,”

Owusu said the city allocated about $10,000 of its budget for tree removal on public grounds at the beginning of the year, but because the disease is so widespread, it will likely require an additional $10,000 at the city level. He is unsure where that money will come from at this time, a decision he says is up to his superiors. Owusu is part of the public works department.

If the elm is on private property, the city notifies the owners via letter, which requires the resident to remove the infected tree within a 14-day period. If the tree isn’t removed within that time, the city contracts a removal service, and later, bills the resident for the incurred cost.

Owusu said there is a five-year payment plan in place for individuals who cannot cover the costs up front.

And while the city admits the problem is worse this year, Robert Keogh, past chairman of Dickinson Urban Forestry Committee, said he believes the number of diseased elms in Dickinson is more widespread than those estimates.

“I can’t even give an exact number,” he said, “but it’s a lot.”

Based off detailed observation, he predicted the number is well over 100 affected trees.

He said it is clear that a tree has been infected by the fungus due to the yellowing, browning or wilting of leaves. A single dead branch can also be an indication that the entire tree has the disease.

“It’s not that noticeable to the uneducated eye right now,” Keogh said. “But by the end of the summer, it will be. There will be a lot of dead trees.”

He said the only way to control the disease is through an aggressive preventative approach, which consumed the majority of his time while on the committee.

Keogh said there were two ways the city would check for the disease. The first approach was through a close monitoring program where a tree would be cut down, chipped and buried during the first indication signs of infection to limit its spread. The second method used was through firewood inspection, where beetles bore under the surface, relocate and transmit the disease to living trees.

Owusu said the fungus is “very hard to prevent” and said the only good method is through planting a diverse range of tree species.

The most diseased trees Keogh ever recorded was nine in a single year, but he said five or six was a common number. This year, he suspects, will be an anomaly.

“It’s going to change the landscape, there is nothing we can do about it,” Owusu said.

Once the tree is infected, there is nothing that can be done, meaning it needs to be killed.

But Owusu said there are plans in place to replace those trees needing to be cut down.

This time, the key will be diversification.

Owusu said American Linden, Prairie Expedition Elm, Russian Elm and Princeton Elm are being looked at as replacement species.

“The key is good management, diversity and active pruning,” Claeys said.