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Dutch Elm Disease

Dutch Elm Disease

Dutch Elm Disease, commonly referred to as DED, is a fatal and highly contagious disease of the elm tree. So far, prevention efforts have kept Alberta free of DED. However, everyone needs to pitch in to protect elm populations in Edmonton, Calgary and throughout the province. Here’s what you need to know.


1. History
Dutch Elm Disease is caused by the fungus Ophiostoma ulmi and is spread by bark beetles. Here’s a timeline of its emergence in Canada.

  • 1930. Infected lumber arrives to North America.
  • 1940. Diseased trees are first reported in Quebec in 1944, although bark beetles responsible for the spread of DED were spotted in the region as early as 1940.
  • 1967. Cases are reported in Ontario. Nearly 80% of all elm trees in Toronto will die.
  • 1975. The disease makes its way to Manitoba.
  • 1981. Cases spread to Saskatchewan.
  • 1998. An isolated case is spotted in Alberta.

Thanks to tremendous prevention, no other cases have been reported in Alberta, and the province currently has the largest population of elms unaffected by DED in the world.


2. What is it?
Dutch Elm Disease is a fungal disease primarily spread by two species of bark beetles who carry the spores from tree to tree. The larvae tunnel beneath the outer bark of the tree, creating distinctive “feeding galleries.” However, the disease can also spread from the roots of an infected tree, meaning the fungus can be present even in the absence of these tunnels.

A tree will try to prevent the fungus from spreading by plugging the tissue used to transport water and nutrients. This will cause the tree to starve and eventually die.


3. Spotting it
Learning to recognize symptoms is crucial. Here are the signs of DED:

  • Leaves suddenly wilting. Since the upper branches are typically the first ones affected, this can be hard to spot.
  • Dying branches and yellow, brown and curling leaves, usually appearing in June and early July.
  • Leaves falling.
  • Brown or red streaks that can be seen in the wood when the bark is pulled back.

DED moves quickly. A small tree can die in less than a month.


4. Controlling it
Prevention is the only way to control DED. Fungicide treatments are available but need to be repeated often and usually only prolong the life of the tree for a few years.

  • Take preventive measures. Ensuring that your trees are strong and healthy is crucial. ArborCare’s experts can help you keep them properly . Make sure to never trim elm trees between April 1 and September 31. Bark beetles are active during this time and are attracted to the smell of cut wood.
  • Care for your trees. Water them regularly from April to August and then only once or twice before the ground freezes for the season. This will help them survive the winter unscathed.
  • Keep your property clear. Get our experts to remove dead elm trees and branches from your property. These are ideal breeding grounds for the bark beetles who carry DED.
  • Respect the law. Remember that it’s illegal to stock elm firewood in Alberta. In addition, you shouldn’t transport elm firewood into or within Alberta, as it could spread DED.


ArborCare can help you stave off Dutch Elm Disease
With over 30 years of experience in Edmonton, Calgary and Kelowna, you can trust ArborCare to take care of your trees. We provide a full range of services and we’re familiar with regulations around elm tree care. Give us a call to learn more about how we can help.

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