Beware the emerald ash borer, an invasive species marching across Canada

Edmontonians are being asked to keep watch for the dreaded emerald ash borer, a deceptively beautiful beetle which threatens to devour the city's canopy of urban trees. 

The bright, metallic green insect is nearly 100 per cent lethal to its host, and the pest is on a steady invasive march across North America. 

Conservationists want to keep the invasive pest out of Alberta for as long as possible, said Jon Sweeney, a forest research scientist with Natural Resources Canada. 

"Once it gets to a place, about 10 years later, more than 99 per cent of the ash in that area have been killed by it," Sweeney said. 

"We're likely going to see it do a lot more damage." 

The beetle, native to eastern Asia, likely came to Canada aboard a ship, stowing away inside untreated wood packing materials.

While it is relatively harmless in its native habitat, the beetle has wrought devastation elsewhere.  

North American ash trees have very little immunity to the beetles. And other than the occasional woodpecker, there are no natural predators to keep populations in check. 

Despite efforts to contain its spread with quarantines and pesticides, the beetle has already killed thousands of trees across Canada, making its way from Ontario through Quebec and into the Atlantic provinces. 

The beetle was first detected near Windsor, Ont., in 2002. In Winnipeg, it was found for the first time last summer.

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Municipalities are doing what they can to slow its spread and delay the inevitable collapse of the ash canopy but the beetle is insidious, Sweeney said.

Borers can live beneath the bark of ash trees for more than two years before obvious signs of infection start to show. 

"It starts out kind of slowly," Sweeney said in an interview with CBC Radio's Edmonton AM.  

"You don't even notice it at first when it's in a tree. It's up in the branches. The tree still looks healthy. 

'Like a bunch of race tracks' 

The insect burrows deep into the trunk of an ash, creating a zigzag of tunnels which erode the tree's ability to feed. 

Within a few years, the tree will yellow and die. All ash species are susceptible, Sweeney said. 

"The tree is completely girdled," Sweeney said. "It just looks like a bunch of race tracks and that's what ends up killing the tree." 

Sweeney said the bug can fly anywhere from 300 metres to 10 kilometres, and is on the lookout for the nearest ash tree where it can begin to populate.

Ash is used as firewood, and that's what could be bringing the beetle further west, Sweeney said. 

"If you've got a cottage or a camp, always use firewood that's sourced locally," Sweeney said. "Don't take firewood and move it there. 

"Just like it came across the ocean on a ship, it got moved by people and that's how it's being spread across North America." 

Edmonton at risk

In Edmonton, the city has posted an information page on its website warning about the beetle.

The city is asking residents to keep watch for signs of infestation and is warning residents against unwittingly spreading the beetle to new territory.

Among all the trees owned by the city of Edmonton, ash are the most prevalent. While they are not native to Alberta, there are more than 88,500 city-owned ash trees lining boulevards across the city. 

'"Approximately 60 per cent of the boulevard trees in Edmonton are green ash. Because of this, much of our urban forest is at serious risk," reads the city website. 

"If left unchecked, emerald ash borer could cause untold costs to our quality of life and local infrastructure. Beetle-damaged trees fall apart with little provocation, damaging houses, vehicles and citizens alike."

Trees which may be infected should be reported to the city. An obvious sign of an infestation is cracked bark. 

The Government of Canada estimates it will cost municipalities $2 billion over the next 30 years to treat, remove and replace ash trees infested with the emerald ash borer. 

"A lot of the responsibility is down to municipalities," Sweeney said. "They're the ones that have dead and dying street trees that they have to take down for safety reasons. 

"They're stuck with it and it costs a lot of money to try and manage this."