Dutch elm disease (DED) Ophiostoma ulmi and Ophistoma novo-ulmi
Dutch elm disease (DED) is caused by a fungus, Ophiostoma ulmi (Buisman) and Ophiostoma novo-ulmi (Brasier), which blocks the tree's ability to conduct water and causes the tree to die.
The fungus is mainly spread by three species of elm bark beetles:
- the smaller European, Scolytus multistriatus (March)
- the banded, Scolytus schevyrewi and
- the native Hylurgopinus rufipes (Eichh)
Other elm bark beetles and root grafts with neighbouring trees can also spread the disease.
Elm bark beetles are attracted to freshly pruned, sick, weak or dying elm trees. The larvae develop in the inner bark. Adults that emerge from infected trees will fly to healthy trees and infect them with the fungus, causing the disease to spread.
All species of North American elm are susceptible. The disease now occurs in most of the natural range of Ulmus americana from Manitoba to the Maritimes, with the exception of Newfoundland and Labrador. Saskatchewan is considered partially infested with Dutch elm disease.
Contact your local Canadian Food Inspection Agency office for additional information.
Elm pruning bans
It is illegal to prune elm trees in the following provinces during periods when elm bark beetles are active. Pruning the trees creates wounds that can attract the beetles and cause the disease to spread.
- Alberta from April 1 to September 30
- Saskatchewan from April 1 to August 31
- Manitoba from April 1 to July 31
Elm species should not be pruned anywhere in Canada from April 1 to September 30 to reduce the risk of further spread within regulated and DED-free areas.
What you can do
- Learn to identify elm trees and locate them around your property
- Take steps to keep trees in good health
- Starting in mid-June, look for the following:
- "flagging": wilted leaves in the upper crown will curl, shrivel and turn brown by late June or July (see images below) and often remain attached to the tree into winter
- "staining" in the sapwood (see image below)
- Report signs of Dutch elm disease on our plant pest reporting page. Branch samples may need to be taken by a trained arborist to determine if an elm is actually infected with this disease.
- Follow municipal or provincial elm wood regulations and guidelines when disposing of elm wood so you don't spread the beetles or the fungus.
- Don't store or transport untreated elm firewood--moving firewood is one of the highest risk pathways for accidentally introducing Dutch elm disease into pest-free areas.
- D-97-07: Phytosanitary requirements for the importation from the United States and domestic movement of elm material (Ulmus spp. and Zelkova spp.) to prevent the introduction and spread of Dutch elm disease Ophiostoma ulmi (Buisman) Nannf. and Ophiostoma novo-ulmi (Brasier) within Canada
- D-01-12: Phytosanitary requirements for the importation and domestic movement of firewood
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