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Black knot fungus has infected several trees throughout Calgary. According to Michelle Irving, communications advisor for the City of Calgary parks department, it is easily spread through wind and rain and is difficult to control.

“Based on how the fungus is spread, cool, wet spring weather from past years may also aid dispersal,” she explained to Canadian Groundskeeper.

Irving said the Prunus species of plants, which include Mayday and Chokecherry trees, are most infected by the disease, which looks like black clumps of coal that wrap around twigs, branches, and even tree trunks.

Although the fungus has been in Calgary for years, the disease has become worse over the last little while, now moving to communities in the southwest of the city.

Richard Pootmans, Ward 6 councillor, told CBC News the city has lost at least 50 trees in Discovery Ridge and they have worked out a cost-sharing agreement with the community association to remove and replant the infected trees along the neighbourhood’s main boulevard.

“We’re going through other communities in West Springs and Cougar Ridge, looking at similar problems, and dealing with this as quickly and as cleanly as we can,” he said.

Irving said the parks department regularly monitors trees for the fungus and manages them by pruning infected branches. They will only remove infected trees if they are in major decline as a result of the fungus and cannot be repaired.