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Reminder: Elm Tree Trimming Season is Coming to an end

Posted on Mar. 25 2021

Provincial Dutch Elm Disease (DED) prevention and control measures are in place April 1 to September 30 and can be enforced under the Alberta Agricultural Pests Act (APA). Elm trees cannot be trimmed or pruned between April 1, and September 30. 

At present, Alberta has the largest DED-free American elm stand in the world. However, its borders are being pressed from two sides by Saskatchewan and Montana, both of which are battling the disease. Once an elm is infected with DED there is no cure, and it must be removed and destroyed immediately.

DED is caused by a fungus that clogs the elm tree's water conducting system, causing the tree to die. The fungus is primarily spread from one elm tree to another by three species of beetles, the smaller European, the native and the banded elm bark beetle. The beetles are attracted to weak and dying trees, which serve as breeding sites for the beetles. Once the beetles have pupated and turned into adults they leave the brood gallery and fly to healthy elms to feed, thus transporting the fungus on their bodies from one tree to the next. Using traps and lures, monitoring for the beetles is done annually in municipalities and campgrounds throughout Alberta by STOPDED. The smaller European elm bark beetles have been found throughout the province in low numbers since 1996. In recent years the banded elm bark beetle has been found, first in the City of Medicine Hat in high numbers and now in more municipalities in southern Alberta.


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 DED suspect elms must be tested in a lab. A confirmed DED tree must be removed and disposed of properly immediately to prevent further spread.

What can you do?

  • Be aware of the Provincial elm pruning ban between April 1 and September 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 elm branches as they can provide beetle habitat only between October 1 and March 31st.
  • Dispose of all elm wood immediately by burning, burying or chipping.
  • Report all suspect trees to the DED Hotline at 1-877-837-ELMS.

What you shouldn't do!

  • Do not transport or store elm firewood at any time!
  • Do not transport elm firewood into Alberta! Firewood is confiscated at all the Alberta-Montana border crossings.
  • Do not prune elms between April 1 to September 30.

DED and the beetles are declared pests under the AB Agricultural Pests Act and these prevention measures are enforceable under this act.

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

Our elms are a treasure that we cannot afford to lose. We must stay vigilant to keep our elms healthy. 

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