LETHBRIDGE — Two trees on the north side of Lethbridge recently tested positive for Dutch elm disease after forestry staff first noticed symptoms in early August, city officials confirmed Thursday.
Samples tested at provincial and federal labs confirmed the presence of the disease, the first known cases of DED in Alberta.
Alberta and British Columbia had been the only provinces in Canada that managed to remain free of the disease since it was first observed in the eastern United States in 1928.
Dutch elm disease poses a serious threat to the health of elm trees, which make up nearly 10 per cent of the urban forest in Lethbridge, numbering around 6,000 public trees and 5,000 private trees.
Due to that seriousness, forestry staff removed and safely disposed of the two trees late last week.
There’s no evidence of how DED arrived in the city but it’s usually introduced into a community by transporting firewood or importing infected trees.
Parks manager Dave Ellis says the urban forest is an important part of the community, and they have been monitoring tree pests and insects for many years to protect it.
“The efforts to control Dutch elm disease and keep it out of the province have been going on for 20 or 25 years, and it’s been a very active effort,” he said.
“Very deliberate on the part of municipalities and the province because it has been devastating where it’s shown up,” Ellis said.
Dutch elm disease is caused by a fungus that can be carried on elm bark beetles when they fly between trees, spreading the infection and causing flagging.
“Flagging is when the leaves on a branch turn bright yellow all of sudden, and that is a classic sign of DED,” said Ellis.
“The branch dies and the leaves turn yellow for no apparent reason.”
The city is now working with the Alberta ministry of agriculture and forestry and the Canadian Food Inspection Agency to develop a response strategy.
Ellis says city council has had the foresight to set aside a reserve to deal with this kind of situation, so there won’t be any impact on the operating budget.
Janet Feddes-Calpas, executive director of the Society to Prevent Dutch Elm Disease, says this is significant for the province.
“We have a prevention program in place that’s been in place since 1975 when the disease was first found in Manitoba. We’ve been very vigilant in Alberta on prevention realizing we do have almost 600,000 trees in the province spread throughout the municipalities,” said Feddes-Calpas.
They feel that DED was most likely brought into the province through firewood that came from an infected area like Saskatchewan or Montana.
“We are vigilant about this at the borders to collect firewood, but there’s still firewood coming in. People are going camping and bring their firewood, and if a tree went down in Saskatchewan there would be a good chance if they took that wood that it would be infected,” said Feddes-Calpas, adding they just want people to be aware of what they can do themselves, and to be aware that since this is happening around the fall there will be surveillance of the trees next year.
Lethbridge has been an active member of the Society to Prevent Dutch Elm Disease since it was first formed.
As the city continues monitoring the elm trees in the public urban forest, they’ve offered a few things residents can do to be vigilant:
Determine if they have any elm trees on their property;
Watch for the signs of DED and report it to 3-1-1;
Refrain from pruning elm trees between April 1 and Sept. 30, and;
Give the tree a good thorough watering before the fall frost to help it stay healthy through winter hibernation.
Do not keep any elm wood for personal use as it’s illegal to do so and stored elm wood is the ideal breeding environment for elm bark beetles.
Elm trees can be injected with a fungicide in the spring to treat DED and the city is now exploring this option.
Staff will work to map the elm trees and assess their condition which will help determine how and if they can be treated.