Dutch Elm Disease

Elm trees make up a significant and important part of the Lethbridge Urban Forest. There are approximately 5,000 public and 5,000 private elm trees in Lethbridge.

Dutch Elm Disease (DED) poses a serious risk to the health of elm trees. The disease is caused by a fungus, which blocks the elm tree’s water conducting system. Once infected, the tree will die in one to two years. There is no cure, only prevention.

Elm bark beetles spread the fungus from tree-to-tree. The beetles breed under the bark of dead or dying trees and, when the new generation emerges, they carry the fungal disease to new trees. It is most often introduced into a community through the transport of firewood.

DED Symptoms

• Early summer – green, wilting leaves
• Mid-Summer – clinging, brown, wilted leaves
• Dark brown or red streaks under the bark

What are we doing to prevent the spread?

In August 2020, two cases of DED were identified in Lethbridge. Since then, the City of Lethbridge has been working with Provincial and Federal agencies to assess the scope of the infection and to develop a response strategy. This began with the immediate removal and safe disposal of the infected trees. There have been no confirmed cases of DED since August 2020.

What can you do?

• Do not store or use elm wood as firewood.
• Adhere to the yearly pruning ban: Do not prune elm trees from April 1 to September 30.
• Follow proper pruning: prune dead or dying portions from October 1 to March 31. Ensure proper disposal of the trimmings by either taking them to the landfill, burying or burning.
• Keep elm trees healthy by watering them from April to August, with one or two good watering's before winter.