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The Asian long-horned beetle could wipe out 40 per cent of London’s trees
April 9, 2017
Randy Richmond

As if the emerald ash borer wasn’t bad enough.

London has a new and nastier villain on the horizon, with the potential to kill 40 per cent of the Forest City’s forest.

“This one has a bigger appetite,” environmental planning manager Andrew MacPherson says.

The Asian long-horned beetle isn’t in the city yet. But city staff are making sure city council and the public known about the threat, with a report heading to council’s planning and environment committee Monday.

“We’ve all been through the emerald ash borer. We can see the damage one insect can do across the city,” MacPherson said.

“If the beetle comes, this will be a more serious threat. It will go for many more species of trees.”

The beetle, known by its acronym ALB, has been spotted in the Toronto region, Massachusetts, Ohio and New York and could get to London in any number of ways, by hitchhiking aboard wooden packaging in rail, air or truck traffic.

The only way to battle the beetle is to destroy the infested trees and others at high risk within a 400-metre radius of a confirmed host tree. A 2003 infestation in the Vaughan/Toronto area led to the removal of 655 infested trees and 28,165 high-risk trees.

The city report gives the beetle its due as a somewhat attractive species — for an insect, at least.

As an adult, it’s “a visually stunning large beetle with a black body, blue-white bands on long attennae (the horns), blue leg bands and a starry sky pattern of white spots of various sizes on its wing casings.”

At no stage is the beetle a friend to trees, however. It starts as an egg laid on the surface of a tree, and in two weeks becomes a larval grub that enters the bark to eat the tissues, full of nutrients, beneath.

After one to year years, the larva emerges from the tree as an adult beetle “by chewing a relatively large, perfectly round exit hole,” about 10 mm in diameter.

“The disruption of the tree’s life support system results in a rapid decline, with crown and branch death within three or four years, and mortality of the tree within 15 years of initial infestation,” the city report says. “Infested trees do not recover.”

The good news is the beetle is not a good flyer and can wing it only about 100 metres from a host tree.

That means once an infested tree is spotted, quick work can limit the damage somewhat.

London set up a mock infestation site in 2014 in Springbank Park to begin educating the public on how to identify the threat, and is training city staff on the signs.

Council has supported early steps to educate the public about the threat, MacPherson said.

The city has a budget of $400,000 a year to replant trees lost to the emerald ash borer, but will need new money if the beetle ever shows up, he said.

“For now, it’s vigilance and preparation.”