Dutch elm disease (DED) continues to be a concern for elm trees across Alberta. This summer, the City of Edmonton has confirmed several additional cases of DED, bringing the total number of confirmed cases in the city to 16 since the disease was first detected there in 2024. While these confirmed cases are well outside Rocky View County, they are an important reminder of why monitoring Alberta’s elm trees remains so important.
Dutch elm disease is a serious fungal disease that can affect all species of elm in Alberta. The fungus blocks the tree’s water-conducting system, causing branches and eventually the entire tree to die. The disease is primarily spread by elm bark beetles, which can carry the fungus from infected trees to healthy elms.
Early Detection is Key
One of the most important ways to help slow the spread of DED is to identify and report suspected trees as soon as possible. Early detection allows infected trees to be tested and, if confirmed, promptly removed before the disease has an opportunity to spread to nearby elms.
Residents should regularly monitor elm trees on their properties, particularly throughout the summer. Early symptoms can include leaves on one or more branches suddenly wilting, drooping or curling. Leaves may turn yellow or brown and remain attached to the branch, creating a condition sometimes referred to as “flagging”. When infection occurs later in the season, leaves may yellow and drop prematurely. These symptoms can sometimes be confused with normal seasonal changes or other tree stresses, so laboratory testing is required to confirm DED.
If you notice an elm showing these symptoms, do not assume it is Dutch elm disease and do not remove the tree yourself. Report the suspected tree so it can be assessed and, if necessary, tested.
Monitoring Helps Protect our Elm Trees
Monitoring is especially important because Alberta continues to have a valuable population of elm trees. Alberta has the largest DED-free stand of American elm in the world, and maintaining this status is important for both our communities and the province’s nursery industry.
The Society to Prevent Dutch Elm Disease (STOPDED), in partnership with Alberta municipalities, including Rocky View County, supports ongoing surveillance for DED and the elm bark beetles that can spread it. Comprehensive surveys are also being conducted in several Alberta communities to improve early detection.
Residents play an important role in this monitoring effort. Taking a few minutes to check the elms around your property and reporting anything suspicious can help ensure potential cases are identified as quickly as possible.
Help Prevent the Spread
There are several ways residents can help protect Alberta’s elm trees:
- Do not prune elm trees between April 1 and September 30. This is Alberta’s annual elm pruning ban. Elm bark beetles are active during this period and can be attracted to the scent of fresh cuts, increasing the risk of spreading DED.
- Keep elm trees healthy and maintained. Remove dead and dying branches during the permitted pruning period, October 1 to March 31, to reduce potential habitat for elm bark beetles.
- Never transport or store elm firewood. Elm wood can harbour elm bark beetles and contribute to the spread of DED.
- Report suspected DED promptly. Do not wait to see if symptoms improve or spread to other branches.
See Something Suspicious?
If you notice an elm with symptoms that could be consistent with Dutch elm disease, contact the STOPDED Hotline at 1-877-837-ELMS (3567). Alberta recommends reporting suspected infected trees immediately.
Dutch elm disease is a serious threat, but early detection and responsible elm management can make a difference. By monitoring the elm trees around our homes, farms and communities and reporting suspicious symptoms, Rocky View County residents can help protect Alberta’s elm trees for years to come.