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Dutch elm disease found in downtown park trees

Dutch elm disease has been confirmed in 13 American elm trees in Kenmare’s downtown park.

7/14/15 (Tue)

Specialist takes a look... Lezlee Johnson, a community forestry specialist with the North Dakota Forest Service in Bottineau, analyzes the curled leaf of an American elm tree in Kenmare's downtown park Friday morning. Johnson identified 13 trees in the park with Dutch elm disease.

By Marvin Baker

Dutch elm disease has been confirmed in 13 American elm trees in Kenmare’s downtown park.

Lezlee Johnson, a community forestry specialist with the North Dakota Forest Service in Bottineau, made that determination Friday morning after analyzing the trees in the downtown park.

“There are a lot of nice trees in that park and they provide a lot of shade,” Johnson said. “We’ll see if any need to be removed.”

The easy solution is to remove the trees, however, there are other options that can be done to save the trees.

Dutch elm disease is best managed by interrupting the disease cycle. The most effective means of breaking the cycle is early and thorough sanitation to limit the population of the insects that transmit the fungus from tree to tree.

The American elm is highly susceptible to this disease and yellows; it is also moderately preferred for feeding and reproduction by the adult elm leaf beetle and highly preferred for feeding by the Japanese beetle in the United States.

Trees grown in Europe have proven very susceptible to damage by leaf-feeding insects in general, far more so than native or Asiatic elms.

American elm  is also the most susceptible of all the elms to verticillium wilt, whose external symptoms closely mimic those of Dutch elm disease. However, the condition is far less serious, and the tree should recover the following year

Other useful means of affecting the disease cycle include using insecticides to kill the insect vector, breaking root grafts between trees, injecting individual trees with fungicides to prevent or halt the fungus, pruning out early infections, and planting Dutch elm disease tolerant or resistant elm cultivars or other tree species.

After finding the disease in downtown Kenmare, Johnson suggested property owners do their own scouting to see if their own trees might have the disease.

Symptoms include dead branches at the top of the tree, or leaves that curl, turn yellow and fall to the ground in mid summer. She said the vector is especially aggressive this time of year.

“The symptoms will come rapidly and you will see wilting,” Johnson said. “We’ve identified these 13 American elm trees with Dutch elm disease.”

Another cause of Dutch elm disease is what Johnson called root wrap. When several adult trees are in close proximity, the roots may wrap around each other as they grow and a fungus called Ascomycota will affect the trees.

“I’ve started a list of trees that will do well in this soil type to increase the diversity in this park and in town,” Johnson said. “Our elms have been living on borrowed time for a long time now.”

Dutch elm disease has been around for years and has destroyed hundreds of thousands of Chinese elm trees that once lined North Dakota’s shelter belts.

Part of Johnson’s list recommends hackberry, a medium-sized tree that can grow to 80 feet and has alternating leaves.

Johnson said an elm tree currently being researched by North Dakota State University is showing a lot of promise in fighting Dutch elm disease.

“It’s the Prairie Expedition Elm that is grown at Absaraka,” Johnson said. “It’s a nice little tree and I think we want that elm look.”

The Prairie Expedition Elm is much like the American elm. It has the same type of leaf and bark and grows to about the same height with a similar canopy. The tree is also very winter hardy.

The big difference, however, is that the Prairie Expedition Elm is Dutch elm disease resistant.

Johnson said she has talked with Arlen Gartner of the park board suggesting the best locations for new trees.

“We don’t want a forest out there,” she said. “We want to keep it a park.”

Johnson said it’s unfortunate that North Dakota’s state tree is susceptible to Dutch elm disease, but the species is hardy and won’t become extinct.

“The American elm will never be completely wiped out,” Johnson said. “It will produce seeds first and will always be a component of the forest, but not as stately.”

After analyzing the trees in the downtown park, which includes several green ash trees that will need to be removed, Johnson inspected the trees in Lakeview Cemetery.

She concluded those trees, mostly evergreens, are in good condition and other than a bit of pruning, will be set for another three to five years.

She said the state Forest Service can assist financially in removing the trees and getting them replaced.

“If the city of Kenmare is interested in taking better care of its trees, or becoming a Tree City USA, we’re in a good position,” Johnson said. “We will have some cost share available.” ... Read EVERY WORD on EVERY PAGE of The Kenmare News by subscribing--online or in print!