Sooty bark disease killing sycamore trees on southern Vancouver Island

A 50-year-old sycamore tree in James Bay is being killed by something scientists says is new to Vancouver Island. It’s called sooty bark disease.

“It will not survive another growing season,” said Joey Tanney, a research scientist with the Canadian Forest Service.

It’s an invasive disease that has been found throughout Europe in the form of a fungus that grows within the wood of the tree. On Thursday, that tree in James Bay was being cut down.

“It produces an immense amount of spores,” said Tanney.

Tanney says the fungus is capable of producing 170 million spores in a single centimetre of bark, trillions of spores on a single tree.

“Over time they gradually wear and they are blown around by the wind,” said Tanney. “They can affect new trees by landing on wounds.”

Sycamore maples were brought to the West Coast from Europe to be ornamental trees. Scientists say the newly found fungus can lay dormant for years and only attacks when a tree is stressed from environmental factors.

“These disease waves typically follow droughts and heatwaves,” said Tanney.

Following the heat dome that gripped Western Canada in the summer of 2022, researchers began seeing signs of the disease throughout the Pacific Northwest.

There are roughly 250 sycamores in Greater Victoria. Thirty of those have been identified as being infected with sooty bark disease.

Now researchers are trying to figure out an important next step: “Whether or not this fungus can actually infect and cause disease in our native maple species, such as big-leaf maple and vine maple,” said Tanney.

Currently, the Pacific Forestry Centre is conducting a greenhouse experiment hoping to find the answer to that question.

“Around this time next year, we will have the answer to that,” said Tanney.

“We need people, in fact, to help us to find these trees, to tell us 'I have a tree in front of my house and it doesn’t look good,'” said Nicolas Feau, a research scientist with the Canadian Forest Service.

An infected maple tree will have dark spores resembling soot on its bark. In the spring, dead patches may become apparent in the form of wilting leaves.

Scientists with the Canadian Forest Service is asking anyone seeing those signs on their trees to contact them, in hopes of stopping the spread.