Dutch elm disease found in Saskatoon tree
City concerned infection could have spread to nearby trees through roots
A single tree in Saskatoon has been confirmed as having Dutch elm disease, which has destroyed millions of trees across North America.
The disease was found in an American elm tree in the Montgomery neighbourhood. City of Saskatoon entomologist Jeff Boone said that particular type of tree is very susceptible to the disease.
"It's one of our most important trees that we have in our forest. We have over 30,000 of them in our city inventory in addition to the private trees," said Boone.
He estimates there are more than 100,000 elm trees in Saskatoon, including privately-owned trees, making it one of the larger forests in North America that has been free from Dutch elm disease. The disease has been present in other parts of Saskatchewan since the 1980s.
2nd case ever in Saskatoon
Only one other case of the disease has ever been found in Saskatoon, in 2015. That case prompted the city to mobilize a response plan.
The city is concerned the new case could have spread to other adjacent trees.
Boone said the city has a dedicated response plan which will begin with the removal of the infected tree on Wednesday.
The city will then begin testing other trees in a 500-metre bubble around the infected tree, as well as visiting homes in the area to look for elm firewood and sample living elms in people's back yards.
It is Illegal to store elm as firewood in Saskatchewan due to the risk of Dutch elm disease.
House visits will first occur in the Montgomery, Fairhaven, Meadowgreen and South Industrial areas. They will then be extended to the King George, Pleasant Hill, Holiday Park and Parkridge areas.
Boone said other prairie cities have been successful in bringing the disease under control.
"One of the nice advantages of prairie communities is that our urban forests are often islands that aren't connected to other larger tracts of elm," Boone said.
"So it means with aggressive management, you can contain and eradicate the disease for periods of time."
Disease destroys 'stately' trees
Boone said Dutch elm disease is an aggressive fungal pathogen which is carried by multiple species of beetle. It can also be transmitted quickly from an infected tree to its neighbours through "root grafts" underground.
He said elms do not grow to the same size in cities where the disease is established as they do in Saskatoon.
"They're still a part of the urban forest but they never become the stately trees that we have in our city," Boone said.
"What happens is they just reach a certain point where they become infected and then they start to decline and basically ... elm populations cycle in a much smaller diameter size."
Signs of Dutch elm disease are more difficult to identify at this time of year because they are similar to changes that occur naturally in fall, such as yellowing and curling leaves.
A news release from the city said trees can start showing symptoms as early as June. Anyone who notices these changes is urged to call the city's urban biological services.
Residents are also asked not to prune elms during a provincial ban between April 1 and Aug. 31 and to dispose of any elm wood at the city landfill.