Residents urged to prepare for loss of trees

A small but destructive emerald green beetle attacking Winnipeg’s urban canopy is making its way through the city and property owners are being warned about impending loss.

About three-quarters of the city’s ash tree population has roots on private property, explained Trees Winnipeg board president Gerry Engel, and over the course of the next 10 years those trees may be taken out by the emerald ash borer beetle.

"The public needs to be aware of the reality of this infestation and what it will do to the urban forest," Engel, an arborist, said. "Of the 356,000 ash trees in the city, based on the City of Winnipeg’s tree inventory survey, roughly 256,000 are on private property."

Engel said the City will be responding to this infestation in public parks and boulevards, but will not be assisting private property owners as it did with Dutch elm disease.

"The awareness is that people need to start planning for it now."

The emerald ash borer (EAB) beetle is an invasive species from China and eastern Asia that was first documented in Winnipeg in 2017 in the St. Boniface area, according to the City of Winnipeg. The wood-boring beetle feeds on and kills ash trees in the Fraxinus genus over the course of its life cycle. The larval stage of the beetle kills the tree by feeding on the tissue beneath the bark, girdling the tree, and cutting of the flow of nutrients and water.

Once the beetle is introduced to an urban forest, there is no way to eliminate the pest.

Trees Winnipeg, a non-profit organization supported by the City of Winnipeg and the province of Manitoba, launched Emerald Ash Borer Preparedness Week on Aug. 12 to inform people about the risks associated with the beetle and what can be done to slow the infestation.

Engel said people who have an ash tree on their private property should begin preparing a plan for its removal and to enjoy it while it lasts. Some high-value ash trees can be treated with a pesticide injection to increase the tree’s resilience to EAB, but that is a short-term solution that will not save the tree from the beetle, Engel said.

"They’re very expensive of course, and it’s important for homeowners to know that those injections aren’t going to save the urban forest," he said. "There’s little that one can do to slow it down."  

The City of Winnipeg is injecting some boulevard ash trees in an effort to slow the mortality of the ash trees and make removals more manageable. The estimated value of park and boulevard ash trees is $437 million and accounts for one-third of the city’s urban forest canopy.

"Unlike Dutch elm disease, where we’ve realized, that over the 30 to 40 years now, we can control it at a reasonable rate of loss... We can’t do that with emerald ash borer," Engel said. "It’s so aggressive and the insects produce so quickly, and move from tree to tree rapidly."

An immediate action property owners can take is to begin planting more diverse species of trees on their lots to account for the upcoming loss of their ash tree, Engel said. Trees Winnipeg runs an annual ReLeaf program that provides homeowners with trees at a subsidized cost and instruction on how to care for the new addition to their yard.

He also recommends consulting an arborist to assess the health of the ash tree and begin budgeting for a future removal.

"When an ash tree dies, it becomes unstable, the wood becomes very unstable very quickly, so they have a tendency to fail, once they die, quickly," Engel said. "It’s really important that they’re removed quickly so you don’t have a high risk of damage to private property or public property."

More information about the Emerald Ash Borer Preparedness Week is available at treeswinnipeg.org/emerald-ash-borer/