July 30, 2014 6:24 pm

Maple trees in parts of the GTA threatened by soil-borne fungi


MISSISSAUGA – Stressed and less established trees in parts of the Greater Toronto area are being threatened by soil-borne fungi.

Anita Chakungal shakes her head in bewilderment while looking at her tree-lined street in Mississauga.

For the past few days – stark changes to the maple trees close to her home have had her asking a lot of questions.

“It’s like fall, what’s happening?” she said. “Our trees are dying.”

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Arborists with the city of Mississauga confirm the trees have fungal infections, says Gavin Longmuir, a forestry manager with the City of Mississauga. Two of the most likely infections he said are verticillium wilt or anthracnose.

The two infections are soil-borne diseases that are thriving thanks to cool, damp conditions.

“It will have an impact,” Longmuir said before adding “not all of the trees will succumb to these infections.”

The worst of the two fungi, is verticillium wilt, Phil DiFlorio, the manager of a Terra Greenhouse in Milton said, it can kill the tree in a year. Anthracnose, DiFlorio said, is slower moving and can be cut out if only a few branches are affected.

Otherwise, the best line of defence from either infection is to keep trees well watered and fertilized. Residents are also asked to remove fallen leaves and branches and dispose of them, but not in backyard compost. The leaves themselves carry the spores so permanent disposal is needed to prevent spreading.

Since the fungi are soil-borne, there is no way to be totally rid of it because a lot of trees become infected when they are planted, Longmuir said.

Longmuir places some blame on a poor soil base in new subdivisions.

“These trees don’t get the soil volume they require,” he said. “The roots can’t establish themselves.”

That leads to weaker trees, which aren’t able to fight off any potential illness, including the fungal spores.

In the city of Mississauga, residents can call 311, to request an inspection of trees on city property and forestry staff will assess the tree and its viability.

“If the trees are not going to be viable and they’re not going to survive, we would replace them with a different species,” Longmuir said, adding oak, hackberry, honey locust and other varieties are likely candidates because they aren’t as likely to fall prey to the same disease.

The priority for the city of Mississauga however is remediation, Longmuir said. Staff may trim, fertilize and water the tree to try to save it before it is declared dead. If a tree doesn’t survive, Longmuir says a replacement could take a year or more.

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