End times for ash trees in southern Ontario

April 8, 2015

By: Simcoe Reformer

The tiny green insect – an invasive species from Asia – has been writing the obituary of local ash trees since the first infestation was discovered at a campground near Turkey Point.

Those who know what to look for see damaged and dying trees along most every concession road, in area parks, and along streets in the county’s towns, villages and hamlets.

“If there’s an ash tree in Norfolk, I can guarantee it has emerald ash borer,” Steve Scheers, Norfolk’s superintendent of forests and cemeteries, said during a drive around Norfolk on Wednesday. “I said it would take four years to spread across the county. It’s been seven years since. It’s full blown.”

The ash borer has scarified the landscape in Michigan and in southwest Ontario near Windsor. It would be devastating if the same thing happened in Norfolk. At about 35%, Norfolk has the highest percentage of forest cover of any municipality in southern Ontario.

Southwest Ontario and Michigan have paid a heavy price because of intensive lumbering practices in the early 20th century. Lumber mills in these areas were in the habit of clear-cutting mature forests, creating an opportunity for wild ash to fill the void. As a result, 70 to 90% of these forests were ash trees by time the parasite arrived.

Norfolk doesn’t face the same challenge. Ash trees account for less than 20% of the county’s forest cover. The pending die-off will be noticeable. However, the countryside is not about to go bald. Native species immune to the pest will infill as ash trees go by the wayside.

Dying trees exhibit distinctive characteristics. If a woodpecker is busy in your neighbourhood, chances are it’s mining grubs from an infested ash. If a tree trunk looks like it’s been clawed up and down by an angry bear, chances are woodpeckers have been hammering on it.

Infested trees also die from the crown down. As this occurs, the root system tries to compensate by putting out sucker branches on the trunk near ground-level.

Varieties about to disappear include white ash, green ash, red ash and pumpkin ash.

For reasons unknown, blue ash stands up to the borer. As a result, they are the only native ash trees with a chance of survival.

(With its bright orange fruit, mountain ash is a popular ornamental tree unrelated to the ash family. As such, it is not vulnerable to ash borer).

The blue ash’s endurance is one of the few good news stories to emerge from the ash borer catastrophe. Another is the fact that ash borer will likely run out of food once it reaches the east coast of Canada. American researchers have been trying to coax the insect into attacking other trees but with little success.

If left with no other food source, the ash borer will make do with the fringe tree, a distant relative of the lilac family. However, there is no evidence lilac bushes are on the pest’s hit list.

Norfolk’s forestry department took down 200 infested trees last year. Scheers expects this to increase exponentially as the infestation approaches its peak.

Many trees will have to come down in subdivisions that were built over the past 20 years. Ash trees are a popular addition to new neighbourhoods because they are hardy, attractive and easy to grow. Scheers has already found evidence of significant ash tree die-back in newer subdivisions in Port Dover and other communities.

By: Simcoe Reformer

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