Oak tree decline in Manitoba getting worse, arborist says

Experts sound alarm on city’s oak tree population Arborists say Manitoba's oak trees have been on the decline for decades, and the problem is only getting worse. Josh Crabb has more.

WINNIPEG — Experts are sounding the alarm over Manitoba’s oak tree population.

The bur oaks, which are native to the area, have been in decline for decades but arborists say the problem is only getting worse.

Gerry Engel, arborist and president of Trees Winnipeg, has been keeping a close eye on a treasured oak tree in his Charleswood neighbourhood for several years.

“Part of the tree has declined,” Engel said, pointing to a weak spot on the trunk of the tree.

The towering tree is estimated to be some 200-years-old, but Engel said it’s in decline and the prognosis is poor. He said it’s a sign of a much bigger problem in the province.

“Overall the last several years we’ve noticed a huge increase in the decline of the health of our oak trees,” Engel said.

According to Trees Winnipeg, visible symptoms of oak decline include the dieback of leaves and major limbs of the tree’s canopy.

Engel said a combination of factors are to blame including an insect that lives in the tree called the two-lined chestnut borer, as well as drought and urban development.

“These trees were here when the communities were built, so we’ve changed their environment entirely,” he said.

One example is the replacement of undergrowth with turf grass, leaving the sensitive root systems of oak trees exposed. Oak decline’s a problem Engel said isn’t getting the same attention as Dutch Elm Disease or the Emerald Ash Borer.

“The oak’s kind of been the silent one but it’s speaking now and it’s showing us and telling us I’m not well, either,” Engel said.

The issue of dying oak trees is one the City of Winnipeg said its urban forestry department has observed and is investigating.

“Multiple samples have been taken by urban forestry and private industry to assess for disease and no causal pathogens have been detected,” the city said. “It is suspected to be resulting from a combination of very dry conditions in recent years, exposure of older oaks to urban conditions, and many years of oak decline, however urban forestry is continuing to investigate.”

The Manitoba government said its forestry branch is also on the case.

“The branch has conducted surveys in areas that are reported to have oak mortality and will be examining those areas in more detail,” the province said. “At this time we are not aware of any new insect or disease that is known to be impacting the oaks population in Manitoba.”

Engel said one solution may be re-naturalization of developed areas.

“I think Wellington Crescent is a great example,” he said. “Take a block or two and naturalize that space under these stressing oak trees and see what kind of an effect that will have going forward.”