Dutch Elm Disease
Dutch Elm Disease (DED) is an introduced, fungal disease caused by a vascular wilt fungus (Ophiostoma ulmi and/or Ophiostoma novo-ulmi). DED affects the conductive tissues of trees. Conductive tissues in trees are like human veins. They carry water, minerals, amino acids and sugars to every part of the tree, like our veins carry blood. Without the flow of these liquids, diseased trees begin to wilt and eventually die.
DED is spread through several pathways: by the movement of wood from diseased trees, through contact with contaminated equipment (i.e. pruning tools), through the trees’ root systems (root grafts), and by bark beetles.
Bark beetles burrow into dying elm trees to reproduce in the fall, and remain there for the winter. In spring, the beetles go in search of healthy elm trees to feed on, carrying Ophiostoma ulmi spores with them and further spreading DED.
Ophiostoma ulmi was introduced to North America in the 1930s as a result of a shipment of lumber that was carrying the fungus. DED made it to Eastern Canada in 1940. It was first recorded in PEI in the late 1970s, and first discovered in Charlottetown in 1996. Since then, the disease has continued to spread. DED is an issue across Canada, except in BC and Alberta where the disease is absent. Montreal streets were once home to over 32,000 elms. Today only a few remain, as a result of DED.