Stopping DED in its tracks

By Lethbridge Herald on June 7, 2025.

City urban forestry technician Lindsay Bell points out some of the features of an elm tree in a northside greenspace in 2020 after two trees that summer were discovered to be infected with Dutch Elm Disease.

Sam Leishman
Lethbridge Herald
Local Journalism Initiative Reporter

Lethbridge’s urban forest is free from Dutch Elm Disease (DED) after a small threat five years ago, and the City needs your help to keep it that way.

Back in August of 2020, lab tests confirmed that two trees planted on public land in the Uplands neighbourhood had been infected. Ethan Champion, one of the City’s urban forestry technicians, says the problem trees were removed immediately, and all the wood was buried at the landfill in accordance with conventional practices.

This was only the second known case of DED in Alberta.

Champion says his team closely monitored about 5,000 elm trees across the city for the next three years until Lethbridge could officially be declared DED-free once again.

“We got pretty lucky,” Champion told the Herald. “It could have been a lot worse. Those trees were called in by citizens. We do rely pretty heavily on citizens to help us monitor the trees. There’s very few [technicians] for 50,000 trees all together. It’s the citizens of Lethbridge reporting weird things happening with trees that point us in the right direction.”

The most noticeable sign of DED, according to Champion, is rapidly wilting and yellowing leaves that stay on the branch during mid-summer. He says if the look of an elm tree has changed by the middle of July, there is a problem that needs to be reported.

If you suspect there may be DED in any part of Lethbridge, you’re asked to contact 311 right away. An urban forestry technician will be sent out to conduct an inspection, regardless if the tree is on public or private land. Samples will be taken and potentially sent off to a provincial lab for confirmation.

Champion particularly stresses that firewood should not be stored or moved around since it is the main contributor to the spread of elm bark beetles. He believes that the 2020 infection may have been caused by firewood that was brought to the city from somewhere else.

An elm pruning ban is also in effect each year between April and October. Champion explained that elm trees release pheromones when they are trimmed that attract elm bark beetles. The beetles carry the DED fungus on their body and are most active during those months.

If the fungus has an opportunity to invade a tree, Champion says, it will no longer be able to properly move sugar and water to where it’s needed.

“It’s more or less a death sentence for a tree. Once a tree is infected, there’s nothing we can do to save it. It needs to be cut down and all the wood material removed as soon as possible.”

DED has been an ongoing risk to urban forests across North America for nearly 100 years. Alberta is recognizing DED Awareness Week between June 22 and 28 this year as a reminder to everyone to do their part to prevent the spread of the deadly infection. 

Suspected infections in any part of the province can also be reported to the STOPDED hotline at 1-877-837-ELMS.