Next tree invasion looming

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This article was published 23/6/2010 (2859 days ago), so information in it may no longer be current.

Bracing for an invasion of tree killers, traps have been set up around the city for the arrival of the deadly Asian emerald ash borer.

The tunnelling beetle that has destroyed millions of ash trees in eastern Canada and the United States is now in Minneapolis — a day's drive from Winnipeg. It will arrive here any day now — on a wooden shipping pallet, in a crate, on firewood or attached to a vehicle, said city forester Martha Barwinsky.

The city has placed sticky, green pyramid-shaped traps high in the limbs of 20 of Winnipeg's estimated 280,000 ash trees to act as sentinels, she said.

The Asian beetle that was accidentally introduced to North America eight years ago is in its flight stage at this time of year, Barwinsky said.

In July, insect control branch crews will check the traps for the borers and make sure they're clear of debris. They'll be taken down at the end of the summer and checked again.

Meanwhile, the Canadian Food Inspection Agency has placed another eight traps in Winnipeg, said Barwinsky. Manitoba Conservation has set up traps in ash trees outside the city, she said.

Many of the traps are near transport companies whose trucks may unknowingly bring the dreaded borer, Barwinsky said.

SDLqWhat they've said in Minneapolis is that, on its own, they travel a one-mile radius per year from the source... they tend to travel a lot faster with human activities," she said.

Truckers, tourists and campers may be harbouring the fugitives whose lethal larvae bore through ash trees, killing them.

"Beetles can hitchhike on vehicles," Barwinsky said.

"The main message is not to transport firewood," she said. Winnipeggers should read up on the signs of emerald ash borer infestation so they can spot them quickly and help stop the spread, she said.

If someone thinks they've found a borer or have an infected tree, they should contact the insect control branch, she said.

The spread of Dutch elm disease 30 years ago prompted people to plant hardy ash trees en masse. Now, with ash under attack, the urban canopy in cities like Winnipeg and Minneapolis is threatened.

The owner of Treehugger Tree Care in Minneapolis said his heart is breaking over the devastating beetle that's now boring its way to Winnipeg.

"It's sad," said arborist Jason Pruett. "We've lost a lot of elms and we're going to lose the ashes."

The Asian emerald ash borer was discovered in Minneapolis last year and has infected trees inside an eight-kilometre area, he said.

"I have a couple of trees under my care now."

Property owners can have the tree removed or treated with a costly, long-term chemical pesticide that's worked in other infected U.S. cities, said Pruett.

"We inject it into the tree," he said. "When the tree transpires, it's bringing things up from the roots towards the branches — the sap brings the chemical up into the new wood."

The chemical — called Tree-age (pronounced triage) — has been approved for use by licensed applicators in a number of American states hit by the emerald ash borer. The key ingredient is emamectin benzoate and its product label warns of its "acute toxicity" for humans. The Tree-age is injected into the trunk of the tree.

"Within six to eight weeks, the emerald ash borer won't be able to find habitat in the tree," said Pruett. The treatment lasts for two years and has to be done for the next 20 years at a cost of about $10 per inch of tree diameter, he said. "You've got to be in it for the long term."

In Winnipeg, Barwinsky said that pesticide has not been approved in Canada to battle the borer. Even if it were, with more than a quarter-million ash trees, there's no way Winnipeg could treat them all, she said.

Scientists are looking at a parasitic wasp that goes after the emerald ash borer, but more research needs to be done.

"We're in a massive learning curve," she said.

"There is no magic bullet."

carol.sanders@freepress.mb.ca

Borer beware

An adult emerald ash borer is 2 cm long and 4 mm wide.

The creamy white larvae are about 15 mm long, 1 mm in diameter.

Adults lay eggs in crevasses in ash bark.

Larvae hatch and burrow into the bark after hatching and dine on the ash, girdling the tree and causing death within two years.

The emerald ash borer emerges in early spring to late summer.

Females lay up to 300 eggs from early May to mid-July.

For more information see http://www.winnipeg.ca/cms/bugline/insect_information/emerald_ash_borer.stm

—— Source: City of Winnipeg

Read more by Carol Sanders.