Dutch elm disease could become worse because of milder winters

Jason Juno

University forest resources employee Colleen O’Connor said an elm tree provided her St. Paul house and yard with shade and free air conditioning for the 20 years she has lived there.

But six weeks ago, the tree was cut down, because it contracted Dutch elm disease from a native elm bark beetle. To prevent the disease from spreading, O’Connor was forced to part with it.

“It’s kind of funny, because we lost our dog six months ago,” she said. “It was our dog’s tree.”

Dutch elm disease could be a bigger problem this year than it has been the last two years, said Patrick Weicherding, the University’s Andover Regional Center regional extension educator.

“I suspect we’re going to have lots of Dutch elm this year,” he said.

That’s because recent winters have been mild, he said. Also, some communities might not have dealt with the diseased trees because of a lack of money or staff, he said.

Partially because people find the shape of elm trees pleasing to the eye, researchers often study the disease, Weicherding said. The tree can handle drought conditions and grows well along city streets, he said.

The University sprays its elm trees with fungicides to prevent the disease, said Les Potts, Facilities Management-Landcare grounds superintendent.

There are approximately 300 elm trees on campus, and this summer saw an increase in elm tree deaths.

One high-profile case last summer involved the Minnesota State Fairgrounds, near the University’s St. Paul campus. Half of the fairgrounds’ 188 elm trees were infected with the disease.

If a tree on campus gets the disease, Facilities Management-Landcare prunes the diseased branch if possible, Potts said. Otherwise, employees cut it down and dispose of it properly, he said.

The disease affects the tree’s tissues, which provide the tree with moisture, Weicherding said. The tree then kills that tissue, cutting off its water supply and essentially killing itself, he said.

Homeowners can watch their trees for early signs of the disease, which include discoloration in the upper areas of the tree, he said. They should report such cases to their city’s officials, he said.

The Urban Forestry Club will also hold a seminar to inform homeowners around the Twin Cities about the disease, said Karl Mueller, the club’s president.

It will be Monday at the St. Paul Student Center Theater, he said. The group is charging admission, he said, because it is a fund-raiser. Professionals in the field will speak, and trees will be available for sale.

The club aims to diversify trees in the urban landscape so that when a disease such as this hits, it will not wipe out large portions of the tree population, Mueller said.

The disease started in Asia and moved to Minnesota from the eastern United States, Mueller said.

Meanwhile, O’Connor and husband Mike O’Connor are hoping to get another tree planted. The city owns the property near the street where the elm once stood for approximately 85 years, Mike O’Connor said. The old tree’s stump would have to be removed before a new tree could be planted. The O’Connors would be responsible for that expense.

“We’re going to bake this summer,” Colleen O’Connor said. “We might need air conditioning.”