Two cases of a disease fatal to elm trees were recently discovered in Lethbridge.
Dutch elm disease is a fungus and will kill an elm if infected, says Janet Feddes-Calpas, executive director of the Society to Prevent Dutch Elm Disease, a non-profit organization.
The disease has killed millions of trees in North America since it was discovered on the continent nearly 100 years ago.
And until now, Alberta had successfully kept out the disease, with only one previous case. That was in Wainwright in the late 1990s.
But in early August, two elm trees growing side by side in Lethbridge tested positive for the fungus.
Someone spotted the trees, which seemed to have the typical symptoms like wilting leaves and flagging, which is when the leaves on a whole branch turn yellow.
“Because of the seriousness of the disease … those trees that were confirmed were removed and immediately buried,” said Feddes-Calpas.
As to how the trees got infected, Feddes-Calpas says the affliction can spread from tree to tree by elm bark beetles or by root grass.
“Pieces of wood could be full of beetles and infested with the fungus, and if they’re brought into Alberta, they can easily fly out to a healthy tree and infect the tree,” Feddes-Calpas said.
In at least the first tree, it might have been caused by firewood, brought in from somewhere like Saskatchewan or Manitoba, where the disease is more widespread, she said.
That was also most likely the case years ago in Wainwright, where she says it was almost certain that the fungus was brought in from fire wood. She says the owner of the property had just come back from Saskatchewan with firewood from Tisdale, where the disease was being fought.
The City of Lethbridge says it has been monitoring tree pests and insects for years, including elm bark beetles, which are common in many Alberta municipalities, according to Lethbridge parks manager Dave Ellis. But so far, none of the beetles found in the southern Alberta city were carriers of the fungus.
“Our urban forest is an extremely important part of our community,” Ellis said in a release.
Spread from root grass is how they guess it might have spread to the second tree, Feddes-Caplas noted.
‘It will die’
In 2017, the elm tree inventory showed there are at least 600,000 growing in Alberta and they’re valued at $2 billion, Feddes-Calpas says.
It’s partly why the disease can present a big problem.
“It is serious. Once a tree is infected, it will die. They have no defence [against] the fungus,” Feddes-Calpas said.
“We’ve been fortunate because we’re watching to the east of us and Saskatchewan has amazing prevention programs and control programs in place, so they’re able to [contain] the disease.”
She says Alberta has been able to learn from other provinces’ battles with the fungus.
What to watch for
In terms of prevention, she says it’s important the public first know what an elm looks like.
The second is to watch for sudden yellowing of a branch with initial symptoms like wilted leaves, followed by curling, turning yellow and then brown.
“The dead, curled leaves tend to persist on the tree,” she said.
I you think an elm tree has it, she says, take a branch out of the infected area and look for brown staining, which indicates the fungus is present.
If people see those signs, she says they should call the provincial hotline or the municipality.