How to protect your trees from Dutch Elm Disease

Dutch elm disease – (referred to as DED) is a costly and deadly disease that affects all species of elm trees in Alberta.

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 beetle species. The beetles are attracted to weak and dying trees, which serve as breeding sites. Once the beetles have pupated and turned into adults, they fly to healthy elms to feed, transporting the fungus on their bodies from one tree to the next.

What can you do?

It is the season to keep your eyes open for DED symptoms. To keep Alberta DED free, STOPDED recommends we stay vigilant and familiarize ourselves with the symptoms of DED to contain the spread. 

Common Symptoms of DED:

  • Leaves on one or more branches suddenly wilt, droop and curl.
  • Leaves turn yellow, then brown and shrivel, but stay on the tree; this is referred to as flagging.
  • DED symptoms can also be seen under the bark of infected branches. When the bark is peeled back, healthy elm wood is cream coloured. But when a tree is diseased, dark brown or red streaks can be seen in the infected sample.
  • DED advances quickly and the affected branch will die as more of the tree becomes infected. You might see dead leaves falling out of season.
  • If the tree is infected later in the summer, the leaves on the infected branch or branches will droop, turn yellow and drop prematurely. Late season infections are easily confused with normal seasonal changes in leaf colour.

For more information about Dutch Elm Disease, to learn how to identify the signs, how to prevent it, and how to care for your elm trees visit the Alberta Website.


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