Arborist working to better understand and treat oak tree decline in Manitoba

WINNIPEG -

Work is underway to learn more about how to heal and treat Manitoba’s oak trees.

Oak decline has long been an issue in the province but the city has said as of late it’s observed that some oak trees have been dying faster.

It’s a problem one arborist has been researching in hopes of finding more effective ways to increase their lifespan.

“So it’s not something that’s suddenly appeared,” said Guy Shelemy of Shelemy Arborist Services. “The factors that contributed to this built up over decades and even centuries.”

For decades, oak trees in the region have been suffering from what’s known as oak decline, which experts say is caused by a combination of factors including landscape changes and drought.

Telltale signs are the leaves and limbs on the top of a tree’s canopy dying, which over time leave it vulnerable to infestations of the two-lined chestnut borer which will eventually kill the tree.

He said while it’s known changes and disturbances to soils are to blame, he’s developing a disease model which he hopes can lead to more effective treatment of oak decline.

“It’s going to be multimodal approach,” said Shelemy.

Both the province’s forestry branch and city’s urban forestry department have recently said they’re aware of the work and are looking forward to learning more about it.

“We’re very interested to see what he finds and what his recommendations are,” said city forester Martha Barwinsky.

Oak decline has long been an issue in Winnipeg but over the past three years the city said it’s noticed trees have been dying faster.

“What we’ve been seeing more recently is, what we believe to be, all of a sudden the oak is dying,” said Barwinsky. “Because in the summertime there’s been mature oak trees that it appears to us all of a sudden the leaves have turned brown and the tree has died and it’s not coming back the following year.”

The city has taken some samples but so far only fungal pathogens—the kind that don’t usually take out a tree—have been found, Barwinsky said.

She thinks it may just be added stress from the severe drought combined with landscape changes—factors already known to cause oak decline.

“Oak in general is very susceptible to any changes in land drainage, any changes to soil conditions in its immediate surroundings,” Barwinsky said.

To help heal and treat oaks in decline some have suggested re-naturalizing developed areas.

Shelemy believes that’s only one part of the solution he’s hoping to develop.

“We can control for insects, we can work with disease, we can work with soils and working with those factors we can increase the longevity,” he said.

According to information on the city’s website, no insecticides are registered to control two-lined chestnut borer.

Barwinsky said it’s best to minimize the level of disturbance around an oak’s root system and soil area as much as possible. The hope being that will relieve stress on the tree to prevent the borer from taking over in the first place.