The only time it is legal to prune elms in Alberta is between October 1 and March 31. The elm bark beetles that carry the deadly Dutch Elm Disease (DED) are not active at this time of year. With the annual elm pruning ban lifted until March 31, 2017, there is time now to do some pruning before the cold weather sets in.
Regular pruning to remove dead wood helps eliminate elm bark beetle habitat. However, improper pruning including topping or removing an excessive amount of live wood is not recommended, as this weakens the tree’s structure and shorten its lifespan. Janet Feddes-Calpas, executive director, Society to Prevent Dutch Elm Disease (STOPDED) reminds gardeners “It’s essential that all pruned elm wood be properly disposed of by burning, burying, or chipping by March 31. And, it’s illegal to store elm firewood since it could be harboring elm bark beetles.”
While Alberta is still free of DED, its borders are being pressed from two sides. Both Saskatchewan and Montana are battling the disease. Once an elm is infected with DED there is no cure and it must be removed and destroyed immediately.
Elm trees can be recognized by their vase-shaped outline and simple leaves with coarsely toothed edges. Alberta has the largest DED-free American elm stands in the world. Since its introduction from Europe in 1930, this fungal disease has killed millions of American elm trees across North America. Feddes-Calpas says “We must stay vigilant to keep our elms healthy. DED can be prevented.”