How to prevent Dutch Elm Disease

How to prevent Dutch Elm Disease

  • Jul. 7, 2019 7:30 a.m.

At present, Alberta has the largest Dutch Elm Disease (DED)-free American elm stand in the world, and it is important to protect this valuable resource worth well over one billion dollars.

The Society to Prevent Dutch Elm Disease (STOPDED) is asking for your assistance to save our beautiful elm trees from this deadly disease.

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 and transport the fungus on their bodies from one tree to the next.

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.

Leaves on a DED-infected elm will wilt or droop, curl and become brown, appearing 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, so if you think you see DED symptoms call the hotline.

What to do:

-Be aware of the Alberta elm pruning ban between April 1st and Sept. 30th. 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 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 not to do:

-Do not transport or store elm firewood at any time. DED and the beetles are declared pests under the Alberta Agricultural Pests Act.

Do not transport elm firewood into Alberta. Firewood is confiscated at all the Alberta-Montana border crossings.

Do not prune elms between April 1st and Sept. 30th.

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

– Alberta Agriculture

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