Invasive fungus that kills oak trees now spreading across Ontario

First Canadian report of oak wilt was in Niagara Falls. Now there have been 3 reports in Niagara-on-the-Lake

In December 2021, an invasive fungus infamous for decimating oak trees was half a kilometre away from the Canadian border.

Last month, oak wilt crossed the border and was spotted in Niagara Falls.

It was Canada's first-and-only sighting at the time — but not any more.

The tree disease has been spotted in Springwater, Ont., north of Toronto and has been reported at least three times in Niagara-on-the-Lake, Ont., according to the federal government.

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"To help prevent the spread of these detections, movement restrictions are in place on affected properties. We are working with other federal, provincial and municipal governments to survey the areas and determine next steps," reads a federal government webpage.

Meanwhile the Canadian Food Inspection Agency is telling people in Niagara-on-the-Lake to check oak trees for any signs of the disease.

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What is oak wilt?

The federal government webpage says a fungus called Bretziella fagacearum causes oak wilt.

It says red oak trees are especially vulnerable and can be killed in a single season.

"Oak wilt is spread naturally through root grafts or beetles carrying fungal spores. Oak wilt does not affect human or animal health," reads the webpage.

oak-wilt/Submitted by Lauren Rogers via CBC

Oak wilt, an invasive type of fungus that can kill a red oak tree in only two to six weeks, has been found in Niagara Region, say experts from the Invasive Species Centre in Sault Ste. Marie. (Submitted by Lauren Rogers)

Richard Wilson, a retired forest program pathologist with the Ontario Ministry of Natural Resources, previously told CBC Hamilton oak wilt is similar to Dutch elm disease, beech bark disease, and white pine blister rust — all of which have done "widespread damage."

Lauren Bell, program manager of the Invasive Species Centre in Sault Ste. Marie, Ont., previously said some signs of oak wilt include:

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  • A white, grey or black fungal mat beneath the mat.

  • Cracking along the bark of the oak tree, which is an indicator of the mat.

  • A sweet, fruity smell, akin to Juicy Fruit gum.

  • Falling leaves or wilting and bronzing edges of leaves, starting at the top of the tree.

oak-wilt-disease/Michigan Department of Natural Resources via CBC

Oak wilt disease was discovered in Belle Isle, Michigan in 2016. It was estimated to have killed as many as 112 trees in late 2021, before reaching Canada. (Michigan Department of Natural Resources via CBC News)

How other cities are preparing

Cities near Niagara, like Hamilton, are bracing for the impact of oak wilt.

Lauren Vastano, a city spokesperson, said Hamilton's strategy is being developed based on a federal response framework.

"This management strategy will also be informed by the lessons learned by city staff in executing the emerald ash borer response plan," Vastano said.

"Forestry staff and arborists have received oak wilt identification training and many environmental services staff are also receiving oak wilt identification training from the project manager of forest health.

What to do to stop oak wilt and how to report it

The federal government says people shouldn't prune oak trees between April and November.

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They also shouldn't move firewood.

If someone spots oak wilt, they should contact the Canadian Food Inspection Agency online.

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Thumbnail courtesy of Michigan Department of Natural Resources voa CBC.

The story was written by Bobby Hristova and published for CBC News. It contains files from Cara Nickerson and CBC News.