City of Hamilton says emerald ash borer has changed city tree canopy

Battling the spread of the emerald ash borer has taken its toll on the urban canopy in Hamilton, Ont. says the southern Ontario city's manager of forestry.

The invasive beetle was first discovered in Hamilton in 2009, said Le'Ann Seely, and an action plan to deal with it was approved by city council the next year. Much of it involves cutting down and removing thousands of ash trees, and replacing them with other species.

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"It is noticeable particularly along the streetscape," Seely said. "There are some areas and some subdivisions [where] ash was the chosen tree for that streetscape years ago ... so we do have some areas where you can really notice.

"There's a lot of standing dead, I'm personally noticing a lot this spring," she continued, adding that since 2010, over 9,000 city ash trees have been removed.

City officials in Thunder Bay announced the ash borer has been confirmed in the city Thunder Bay council is slated to receive recommendations July 18.

In Hamilton, Seely said, the young trees planted to replace the destroyed ash largely haven't had time to grow up to get to the height of their predecessors.

In Thunder Bay, city forester Shelley Vescio has said that ash trees make up about 25 per cent of the city's street trees.

Hamilton tree treatment has had 'mixed results'

Vescio told CBC News that treatment of ash trees will be part of the recommendations, along with removal and replacement, that will go to city council this month.In Hamilton, Seely said treatment has been used "selectively."

"They have to be good candidates for treatment, they have to be in a relative level of health that they would respond to it," she said. "We've been treating ones that show to be highly-valued trees."

She said monitoring has shown that treating the trees slows down the ash borer's progression, but generally doesn't kill the beetles.

"It's a naturally occurring phenomenon, so it's hard to know definitely the right approach," she said.