Majestic trees threatened by Dutch elm disease

Here are tips for spotting this devastating disease and preventing its spread

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Alberta Dutch Elm Disease Awareness Week concluded on June 28.

“American elms are planted extensively in Alberta and throughout the years have become the tree of choice for the Prairies with good reason,” said Janet Feddes-Calpas of the Society to Prevent Dutch Elm Disease (STOPDED) executive director.

“These giants with their height and broad vase-shaped canopies have given them tremendous esthetic value. They are tough, can endure extreme heat, cold and drought, yet retain incredible beauty.”

However, all elm species that grow in Alberta have an Achilles heel.

“They are prone to DED, which is a deadly fungus. This fungus clogs the elm tree’s water-conducting system, causing the tree to die in a short period of time. The fungus is primarily spread from one elm tree to another by elm bark beetles.”

Leaves on a DED-infected elm will wilt or droop, curl and become brown. This appears in mid-June to mid-July. Leaves on trees infected later in the season usually turn yellow and drop prematurely. Leaf symptoms are accompanied by brown staining under the bark. All suspicious elms must be tested in a lab, a service STOPDED funds.

Monitoring for the beetles is done annually throughout the province by STOPDED. The smaller elm bark beetles have been found throughout the province in low numbers and now the banded elm bark beetle is found in larger numbers throughout the City of Medicine Hat and area.

What can you do to help?

  • Be aware of the Alberta elm-pruning ban between April 1 and Sept. 30. The beetles are most active at this time and can be attracted to the scent of fresh tree cuts, possibly infecting a healthy elm.
  • Keep your elm trees healthy and vigorous. Water elms well from April to mid-August. To allow the tree to harden off for the winter, watering should be stopped mid-August followed by a good soaking or two before freeze-up.
  • Remove dead branches and trees as they can provide beetle habitat, but only between October 1 and March 31.
  • Dispose of all elm wood immediately by burning, burying or chipping.
  • Report all suspect trees to the DED hotline at 1-877-837-ELMS. A confirmed DED tree must be removed immediately to prevent further spread.

What you shouldn’t do:

  • Transport or store elm firewood at any time. DED and the beetles are declared pests under Alberta’s Agricultural Pests Act making it illegal to do so.
  • Bring elm firewood into Alberta. Firewood is confiscated at all the Alberta-Montana border crossings.
  • Do not prune elms between April 1 and Sept. 30.

To report a DED suspect elm tree or for more information, call the STOPDED hotline at 1-877-837-ELMS or go to

“Our elms are a treasure that we cannot afford to lose,” said Feddes-Calpas. “DED can be prevented.”

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