Edmonton braces for pest that has decimated ash tree populations to east, west

Traps are expected to go up around Edmonton this week to capture the emerald ash borer.

The shining and dangerous pest is poised to wreak havoc on Edmonton’s $400-million population of ash trees, and the city has two staffers working full time to detect any advance here as the invasive bug closes in from the west or east into Alberta.

“We have the largest percentage of our urban forest canopy in green ash of almost any city in North America,” said Michael Jenkins, senior scientist with the City of Edmonton.

Article content

Ranging from 8.5 mm to 14 mm long and 3.1 mm to 3.4 mm wide, the beetle is difficult to spot.

Within a decade of its establishment in a population, 99 per cent of the ash trees die, according to invasivespeciescentre.ca.

“A single piece of firewood can destroy millions of trees,” warns a poster depicting a stack of ash firewood as dynamite sticks with an emerald ash borer at the tip of the fuse.

Ash has been an ideal boulevard tree in cities like Edmonton and Calgary, where urban planners have a very short list of trees that can do well with northern winters.

Most of Edmonton’s neighborhoods built in the Baby Boom 1960s and 1970s were entirely ash, and one-quarter of our urban forest canopy — 180,000 (40 per cent) of the boulevard trees — are green ash, Jenkins said, noting that in period neighbourhoods like Westmount, Inglewood and Prince Charles, nearly 100 per cent of the boulevard trees are green ash, playing their role in storm water management.

Article content

Overland flooding has been observed in areas where the urban forest is decimated by pests.

Deadly origin

The emerald ash borer was likely inadvertently imported to Detroit in infected wooden packing materials from China in the 1990s.

At its epicentre, Ontario, it blew past a feverishly cut fire break-style buffer zone swath of 30 kilometres, working its way to the Atlantic provinces.

In its destructive path, emerald ash borer devastated millions of trees — and the baseball bat industry — and impacted the manufacture of everything from electric guitars and coffee tables to hockey sticks.

The emerald ash borer was found in 2018 in Winnipeg. By 2023, it had leapfrogged on infested wood products to British Columbia’s Lower Mainland.

Since the beetle can only fly 15 km, it’s likely to land in Alberta in its preferred taxi, secreted in firewood, packaging, pallets and cable spools.

Article content

Article content

Corrugated triangular prism plastic traps play on the beetle’s lust for lime green and deep purple colours, while funnel-shaped lime green traps stack in bunches, using pheromones to lure the beetles.

City staffers follow pruning crews, taking branches back to the lab, skimming the bark off and looking for “galleries” where the phloem and xylem move nutrients around in the tree.

That’s where long, skinny emerald ash borer larvae dwell for two years, excavating and munching, their only predator the woodpecker.

The larvae starves the host tree to death, girdling and strangling it by cutting off water, nutrients, all the carbohydrates the tree needs to create leaves and survive.

They emerge as a bright metallic green beetle to look for new trees to nest in.

Leaves and branches die back, eventually leaving the dead tree standing, brittle and weak, easy to knock over, making a 25-foot tall tree with a three-foot trunk an arboreal bull in a china shop.

Article content

Aggressive bug

The curve of the emerald ash borer invasion is aggressive, said Sacha Curran, a project organizer for Community Field + Forest.

“You’re going to start to notice that there’s going to be some trees in your neighbourhood that are going to start to die. But most people won’t start to notice ash trees starting to look unwell until probably 40 or 50 per cent of the tree’s already dead,” Curran said.

Gardeners may be more familiar with Dutch elm disease. Quickly regulated by provincial governments, it’s borne by beetles with a fungus on their outer shell that will kill elm trees.

But the emerald ash borer is likely eight to 10 times more destructive than Dutch elm disease, Curran said.

At a tree symposium this spring with the Alberta Nursery Association, there was signs of scrambling, Curran said.

“When we look at the Alberta nursery industry and the trees that they’re growing and cultivating for municipalities, the ground is shifting underneath them. As we speak, they’ve invested millions and millions of dollars into supporting municipalities and growing the trees they’re asking for,” she said.

Article content

The Canadian Food Inspection Agency protects against invasive species under the Plant Protection Act.

According to Landscape-Alberta.com, the province of Manitoba proactively developed a provincial emerald ash borer response plan in April 2017, listing it as a declared pest under their Forest Health Protection Act, which recommends a “slow ash mortality” approach to the threat.

The “slow ash mortality” approach includes injecting a percentage of eligible trees with a botanical pesticide registered for use in Canada, and other trees are removed as they die, and get replaced.

Although emerald ash borer is on watchlists like the priority invasive and migratory insects in Alberta report, Curran is hoping the Agriculture minister will officially name it a destructive pest, as others have done.

While the emerald ash borer is CFIA-regulated, putting it on the Alberta Agriculture’s official destructive pest list would release a host of management tools for municipalities, she said.

Article content

“Everyone is just kind of waiting for this to be regulated, and it’s just not,” she said.

If categorization as an ornamental threat, affecting urban environments, rather than a crop threat, sounds lightweight, it’s not, Curran said.

When emerald ash borer strikes, its impact will be magnified if Alberta doesn’t get proactive, Curran said.

“Once we have it declared a formal pest, that can release funds and place quarantines on wood movement. It’s a cascading effect,” she said.

From an ecological or an environmental value, trees are sustainable in terms of biodiversity, with pollinators, food and shelter for hundreds of species of insects and other creatures, Curran said.

“They cool our communities and create shade, they help to clean the air by filtering pollution and micro pollution, especially near our road sites like nitrogen oxides and ozone.

Article content

“Urban forests strengthen community connections, they encourage social interaction. Having trees around it increases our feelings of wellness and safety, promoting physical activity, healthy hearts and healthy blood pressures, reducing stress anxiety,” she said, citing studies that show trees have a beneficial impact on traffic slowing, crime rates and incidences of violence.

Curran points to the federal two billion trees program, with its aims for sustainable tree planting.

“I know that municipalities in Alberta are falling behind despite the federal injection of monies for tree planting programs and naturalization,” she said.

“When we look at our urban forest asset management plan, we can’t keep up with the number of trees that are being lost,” she said, citing climate change with the extension of summers and frost-free zones, increases in traffic and population and resulting budget strains.

Article content

“They’re such a mainstay, and my concern is that we’re going to lose these trees really, really quickly, and people won’t know what we’ve lost until it’s gone,” she said.

Alberta Agriculture was not available for comment during the weekend.

jcarmichael@postmedia.com

Bookmark our website and support our journalism: Don’t miss the news you need to know — add EdmontonJournal.com and EdmontonSun.com to your bookmarks and sign up for our newsletters.

You can also support our journalism by becoming a digital subscriber. Subscribers gain unlimited access to The Edmonton Journal, Edmonton Sun, National Post and 13 other Canadian news sites. The Edmonton Journal | The Edmonton Sun

Article content