What is Dutch elm disease?
Dutch elm disease (DED) is a serious disease the of American elm (Ulmus americana) caused by fungal pathogen Ophiostoma (novo) ulmi. The disease was introduced into North America in the 1930s, and has wiped out millions of elms across Canada and the United States. While the disease has been present in Saskatchewan since the 1980’s, Saskatoon is currently free of the disease.
Urban elms are particularly vulnerable because they are exposed to harsh growing conditions due to construction damage, soil compaction, pollution, global climate change, etc.
What does a tree with Dutch elm disease look like?
American elm trees with Dutch elm disease may start showing symptoms as early as June. Typically, the leaves will start to wilt and turn yellow, then curl and turn brown.
If you start to notice any of these symptoms, please call the City of Saskatoon Pest Management Section at 975-3300.
How is Dutch elm disease spread?
In Saskatchewan, Dutch elm disease is spread by the native elm bark beetle. This tiny beetle is able to fly up to two kilometres as it searches for healthy elms to feed on. The Dutch elm disease fungus has tiny sticky spores that stick to the body of the beetle when it is breeding. Bark beetles that fly from a tree that has Dutch elm disease will carry these spores to healthy trees when it feeds or over winters.
What is the life cycle of the disease?
Elm bark beetles spend the winters as adults burrowed into the base of elm trees. In the spring they emerge, flying to the crown of healthy elm trees where they feed. They then fly to elm trees that are sick or dying to breed and lay eggs. The eggs hatch and larvae feed on the inner bark of these trees. By the fall, the larvae turn into adults, emerge from the tree and fly to a new elm to over winter. If the tree they fly from has Dutch elm disease, there is a very good chance the adult will spread the disease to its new host.
What You Can Do:
In 2005, provincial legislation extended the ban period (when pruning all elm trees is prohibited). Do not prune elm trees from April 1 to August 31. The ban covers the period when elm bark beetles are most active.
Outside the ban period, regular pruning helps keep trees healthy and better able to resist all types of diseases, including Dutch elm disease. Removing dead wood also makes your trees less attractive to elm bark beetles.
The new provincial regulations also require an application and authorization to prune, store, use, market or transport elm trees. Please see below for more information.
Responsible tree maintenance protects not only your trees, but all the elm trees in your neighbourhood.
The Dutch Elm Disease Regulations, 2005:
The Government of Saskatchewan legislated The Dutch Elm Disease Regulations, 2005.
For more information on Dutch Elm Disease
SOS Elm Coalition
Canadian Food Inspection Agency - Dutch Elm Disease
Saskatchewan Dutch Elm Disease Association