Dutch elm disease identified in one Saskatoon tree
One case of Dutch elm disease (DED) has been confirmed in Saskatoon. An elm sample sent to the provincial lab by the City’s Urban Biological Services staff has come back positive for DED. This case is the third case of DED since 2015.
In accordance with the City’s DED Response Plan, which requires immediate removal of all positive trees, crews will begin tomorrow removing the infected tree located in Leif Erickson Park in the Westmount neighbourhood. The surveillance and testing program continues to assess elm trees in this area and throughout the city. Based on the results of further testing and proximity of adjacent elm trees, there may be a requirement for further removals.
“This discovery of Dutch elm disease demonstrates that our ongoing surveillance and screening procedures work,” says Darren Crilly, Director of Parks. “Our response plan has been effective in ensuring we identify diseased trees early on, limiting the spread of the disease through rapid removal.”
Saskatoon’s DED Response Plan requires:
- Immediate removal of all positive trees
- Disposal of infected trees at the City landfill
- Sampling of adjacent trees
- Surveillance and testing of private and public trees in the surrounding area with an intensive search for elm material and other sources of infection
“Dutch elm disease is a serious disease of the American elm, and elm makes up about 25% of Saskatoon’s urban forest” says Sydney Worthy, Entomologist. “The disease was introduced into North America in the 1930s and has since spread mainly through the transport of firewood and lumber. It has wiped out millions of elms across Canada and the United States and has been present in Saskatchewan since the 1980s. Saskatoon had a reposted case in September last year.”
The disease is caused by two closely related species of fungi, both of which are transmitted by elm bark beetles and tree to tree through root grafts. It blocks water movement and eventually leads to death of the entire tree. It only impacts elm trees and no elm species is totally resistant.
A tree can be infected:
- By elm bark beetles that transmit the disease
- Through root grafts between trees
- By pruning tools
American elm trees with DED may start showing symptoms as early as June. Typically, the leaves will start to wilt and turn yellow, then curl and turn brown. Residents who start to notice any of these symptoms, are encouraged to call Urban Biological Services at 306-975-2890.
The most effective management strategy for DED is to not transport or store elm wood. Infected firewood is the most likely way that DED would be brought into Saskatoon.
Last year, Parks inspectors issued 71 infraction notices (46 of which contained elm firewood) and removed over 13 tonnes of elm wood from private property. Inspectors also found several instances where wood was moved from elsewhere with elm bark beetle activity in the wood.
Residents can help prevent DED by:
- Not pruning elms during the provincial pruning ban (April 1 to August 31)
- Not storing or transporting any elm firewood – Provincial regulations prohibit the storing or transporting of elm firewood
- Disposing elm wood at the City Landfill
“Unfortunately, because Saskatoon is isolated from other elm forests, our healthy trees get DED because people bring in and store wood from other areas that have beetles that spread the infection. This is why no one should do this – it will kill our much-loved elms.”
For more information on DED, visit saskatoon.ca/dutchelmdisease.