City crews teamed up with national pest scientists this week to diagnose the extent of Winnipeg's emerald ash borer beetle invasion, a budding issue that could end up costing taxpayers hundreds of millions of dollars.

The first confirmed case of emerald ash borer beetles in Manitoba was confirmed in a boulevard tree on Cote Street, in Winnipeg's St. Boniface neighbourhood, in November.

Colin Desrochers and Richard Featherston live in the leafy neighbourhood. Neither were thrilled to know the area could lose its ash trees.

"Having the trees with the canopies it's just fantastic here, so hearing about the beetles, it's devastating," said Desrochers.

"The trees are part of the charm of St. Boniface," said Featherston.

"That's why we bought in this neighbourhood, so a little disappointed that we may lose a lot of our trees."

City forester Martha Barwinsky assesses the damage left by emerald ash borer beetles on a tree in St. Boniface Wednesday. (Holly Caruk/CBC)

Pest biologists with the Canadian Food Inspection Agency arrived in Winnipeg this week to help guide forestry crews through the first phase of diagnosing the problem.

The CFIA monitors pest invasions and regulates efforts to curb the spread of borers. As per its protocol, the first step for a municipality after an invasion is confirmed is to do ground surveys.

Those started at "ground zero" on Cote Street Tuesday, city forester Martha Barwinsky said.

Telltale signs

A team of about 30 workers from the city's forestry branch began surveys on foot Tuesday. They started at the site of that first infected tree and fanned out in a one-kilometre radius, inspecting trees on public property for signs of the carving "galleries" left beneath the bark by borers.

Serpentine tunnels under the bark where the larvae have travelled are signs of emerald ash borer infestation. (CBC)

On Wednesday, Barwinsky and the crews spread out to surrounding neighbourhoods and conducted more surveys from vehicles.

She says the team has already come across several other trees that look suspicious and may have broods of borers quietly gnawing away beneath the bark.

"It really is too soon to tell" how bad the spread is, Barwinsky said. "We think we found it in a few other trees."

Apart from direct signs of infection, surveyors are paying attention to high woodpecker activity in the area. Winnipeg is home to a handful of woodpecker species, and research in the U.S. has shown borers often end up on the birds' menu.

Emerald ash beetles bored their way through this tree in St. Boniface. (Holly Caruk/CBC)

Other indirect signals include "epicormic shoots" — tiny new branches growing out from behind tree bark — and D-shaped exit holes left behind by borer larvae.

350,000 trees at risk

Though its tiny size and shiny green carapace might not look intimidating, emerald ash borers have cost municipalities across North America billions of dollars since the insect was first detected here in Detroit and Windsor, Ont., in 2002.

Winnipeg has been preparing for an invasion for about a decade and was put on notice last year when the beetles popped up in Thunder Bay, Ont., less than 700 kilometres east of the city.

Borers can live beneath the bark of ash trees for more than two years before obvious signs of infection start to show. (Holly Caruk/CBC)

An estimated 102,000 ash trees live in Winnipeg parks and on the city's boulevards. When you factor in all the benefits they confer — things like rainwater run-off prevention and the shade and beauty they provide — the "value" of those trees is up around $437 million, according to the city. A 2012 study estimated the cost of cutting down and replacing those trees at $200 million alone.

There are another 250,000 ash trees on private property in the city.

Left unchecked, 99 per cent of the time a borer invasion virtually destroys an ash population in less than a decade, according to Natural Resources Canada.

'Serious matter for the city'

The first surveys in Winnipeg were expected to be done by Thursday. Experts from the Canadian Forest Service are flying to Winnipeg in January to help train city crews on more precise branch-sampling methods.

Barwinsky said she is hoping the beetle is involved in a two-year, rather than one-year, life cycle because that would increase the odds that the spread will move slower, and buy the city some time.

"How quickly it spreads and how long we're really going to be managing that first cycle, we don't know yet," she said.

"It's a serious matter for the city."

The forestry branch will submit a report to city council by February that lays out a management plan and prices out how much control efforts will cost in 2018.

One species of the parasitic wasps released in other areas to fight emerald ash borers, the Oobius agrili, will lay eggs inside the eggs of the emerald ash borer. (Houping Liu/Michigan State University)

Canadian researchers experimented with the release of hundreds of parasitic wasps last year that take down borer larvae. Barwinsky said it's too soon to say whether something like that will be implemented in Winnipeg.

The best thing homeowners can do to help prevent the spread is to report trees they believe are infested to the city and not move any ash firewood they have stockpiled.

The 2,000 dots on the map below are a random sample of Winnipeg's green ash trees, the second-most common tree in the city. The data reveals although the tree was widely planted across the city, there are high concentrations in newer neighbourhoods, which experts say are likely to become the problem areas with the appearance of the emerald ash borer in Winnipeg.

View the map on mobile here.

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