Elm Pruning Ban
Dutch elm disease (DED) is a deadly disease that can affect any elm tree. Since its introduction from Europe in 1930, it has destroyed millions of American elm trees across North America. DED is prevalent in Manitoba, Saskatchewan and Montana. At present, Alberta has the largest DED-free American elm stands in the world. A total of 219,334 elms, worth $634 million dollars, grow in Alberta’s urban areas.
“Although Alberta remains free of DED, with two neighbouring jurisdictions, Saskatchewan and Montana, battling the disease, we must stay vigilant to keep our elms healthy,” says Janet Feddes-Calpas, executive director, Society to Prevent Dutch Elm Disease (STOPDED).
To reduce the risk of DED, pruning of elm trees is prohibited throughout Alberta each year from April 1 until Sept. 30. Fresh cuts from pruning may attract the beetles that can spread the disease, increasing the chance of an infection. Once they have infected an area, elm bark beetles will feed on healthy elms during the growing season, and then breed over winter in dead and dying elm trees.
“The annual pruning ban is in effect during the time of year when elm bark beetles are potentially most active,” says Feddes-Calpas.
“Pruning remains an important part of regular elm tree care and is encouraged in Alberta, before and after the annual ban period (from Oct. 1 to March 31),” notes Feddes-Calpas.
“Proper pruning helps keep trees healthy and better able to resist disease.” The removal of dead and dying elm wood through pruning also helps to reduce beetle breeding habitat and control any potential beetle population. Prompt and proper disposal of the pruned wood is also essential to keep DED from spreading.
“A professional arborist can determine what type of pruning is necessary to maintain or improve the health, appearance and safety of your trees,” says Feddes-Calpas.
“Topping or removing an excessive amount of live wood is not recommended as it will weaken the tree’s structure and shorten its lifespan.” It is essential that all dead wood be removed and properly disposed of by burning, burying or chipping by March 31 of each year. It is also illegal in Alberta to transport or store elm firewood.