LONDON — Ken Marchant’s first encounter with the beetle that would shape the rest of his career came on a Sunday afternoon in July 2002 while he was watching a Blue Jays game on TV at his home in Guelph. A friend dropped by: a forester with the Ontario government, he wanted Marchant, then a quarantine biologist with the Canadian Food Inspection Agency, to look at some perplexing samples. Marchant forgot all about the game as they peered at preserved larvae and a collection of photos showing a centimetre-long emerald-coloured beetle — he’d never seen anything like it.
The insect had been spotted crawling out of an ash tree in Windsor. When biologists took a closer look, they found it wasn’t alone: similar bugs had taken up residence in trees throughout the city. After peeling back the bark, they discovered spiralling larvae tracks that looked like they’d been carved out by a router. It soon became obvious that few, if any, of the infected trees would survive.
But what was the mystery beetle? Scientists combed through the Smithsonian Institution’s huge collection of insects and came up with nothing. Eventually, they were able to trace the insect to China — it had apparently come to Canada by stowing away on wooden shipping pallets. In Asia, the insect isn’t considered a major pest, as it attacks only weak or sickly trees. In Windsor, though, any ash, regardless of its health, became fair game.
A bi-national science advisory committee tasked with figuring out how to manage the insect gave the emerald ash borer its name. All levels of government joined forces to try to bring it under control. Fifteen years later, the battle continues. New research offers some hope, but time is running out. In September, the International Union for the Conservation of Nature, the world’s largest environmental network, added five of six North American ash species to its critically endangered list because of the ash borer.
Five varieties of ash grow in the province— black, blue, pumpkin, red, and white, with the last being the most common. Some southwestern Ontario forests were 90 per cent ash before the borer’s arrival, thanks in part to the fact that ash is usually one of the first trees to spring back after major disturbances, such as fire and clear-cutting. Because it grows rapidly and can thrive in built-up environments, it’s been a favourite of urban tree-planting programs. Its wood is used for everything from garden tools to hockey sticks to guitars; black ash is a prized basket-making material for Anishinaabe and many other First Nations peoples.
In the spring of 2003, months after Marchant’s first encounter with the insect, workers began removing tens of thousands of ash trees in Essex and Chatham-Kent counties. The goal of the effort, which was coordinated by the Canadian Food Inspection Agency, was to create what’s known as a firebreak, a cleared area of land that prevents the spread of fire. Cities in the United States had used them successfully to combat a different threat: the Asian longhorn beetle — another invasive pest that targets trees.
The experts involved recognized the urgency of the situation. It’s difficult to detect the presence of the ash borer. “Trees only show distress or any symptoms at all when they’re about ready to die,” Marchant explains, “so they can be heavily or moderately infested and show no symptoms until it’s too late.”
Yet many residents of the area objected. They worried their property would be damaged and questioned the need for such a drastic move.
Lyle Phelps, who lives near Merlin, a small community west of Chatham, recalls that in one day, contract loggers felled more than 3,000 trees on his 16-acre property — some of them weren’t even ash. “It looked like they set off a nuclear bomb.”
Marchant defends the decision to make a pre-emptive strike. It was based on the best science of the time, he says. But the biologists had underestimated how difficult it would be to stop the ash borer from being moved in firewood and nursery stock. A year and a half after the firebreak operation, agency inspectors found the insect in Dutton, a municipality about 50 kilometres west of London, and in Lambton County, just north of Chatham-Kent. By 2006, it had arrived in London.
Marchant wasn’t surprised, but he was dismayed. When the insect was found in Ottawa in 2007, he recognized that the quarantine effort had failed. A year later, the government scientist retired.
“I had the years in, and I was extremely burnt out by that time, as were all the other people involved,” he says. “It’s just like a war effort.”
Today, there are 240,000 hectares — an area nearly three times the size of Toronto — of dying ash across southern Ontario. The insect has now spread north to Thunder Bay and east to Quebec.
Biologists liken the leading edge of new infestation to a tsunami. “All we’ve ever seen for emerald ash borer [in North America] is what we call an epidemic population,” says Chris MacQuarrie, a research scientist with the Canadian Forestry Service.
Natural Resources Canada estimates that the cost of removing and replacing ash trees in Canadian municipalities could reach $2 billion over 30 years. (Researchers and government officials say calculating a dollar figure for past efforts is nearly impossible because so many groups have been involved.)
“The emerald ash borer is the most expensive exotic forest insect ever introduced to North America in terms of its economic impact,” says Daniel Herms, a professor at Ohio State University and a leading expert on the insect.
Preventative measures and control agents have been developed in an attempt to limit the ash borer’s spread. The Canadian Food Inspection Agency started a nation-wide campaign to control the transporting of firewood out of local areas. The province surveys forests annually for signs of infestation. Researchers have begun to release parasitic wasps, native to Asia, to prey on ash borers. Insecticides aren’t a viable option: the two registered for use are too pricey to treat large volumes of forest trees.
Although researchers continue to search for surviving native trees to propagate and test for resistance, they’re also exploring alternatives to preserving existing trees, such as cross-breeding North American species with an Asian ash variety that is resistant to borers.
Since 2004, scientists and foresters have been collecting seeds and sending them to the National Tree Seed Centre’s facility in Fredericton, New Brunswick, where they’re dried and then stored at temperatures of -20 C, ready for future planting in more favourable circumstances.
This year, the centre partnered with the Invasive Species Centre in Sault Ste. Marie and the Kemptville-based Forest Gene Conservation Association on a seed-collecting initiative in the Algoma and Thunder Bay districts. “Up here, farther north, there is a unique ash genotype — the trees are a little more cold tolerant than they are in other regions of the province,” explains David Nisbet, the partnership and science manager at the Invasive Species Centre.
At the Devonwood Conservation Area in Windsor, ash-tree roots survive, 15 years after the infestation. They regularly produce saplings, but the borers attack once the trunks are about as big around as a human wrist. Moss and fungi cover the remains of trees that were cut down after they died because of a risk they’d fall on conservation area paths. Their loss created gaps in forest cover that become new homes to other tree and plant species. In one spot, maple has moved in — researchers predict that maple will become more dominant in forests as ash is lost. These gaps, though, also create expansion opportunities for other invasive plants, such as buckthorn and Phragmities australis.
Only time will tell what kind of effect the loss of ash will have on local ecosystems. Ash-leaf litter contributes nutrients to the soil floor, and the tree’s seeds are a plentiful food source for birds. Ash growing near water are also an important source of food for water-based invertebrates such as stoneflies and mayflies.
Those engaged in the fight against the ash borer, however, say it would be premature to conclude that the infestation will lead to a blanket extinction of ash across North America.
To date, the insect has infested only a small proportion of the continent’s ash population, Herms explains. But, he says, it is likely that ash will be reduced to “functional extinction” — becoming so rare in a forest that it can no longer play its established role in the ecosystem.
MacQuarrie says there’s a chance ash may largely disappear in southern Ontario, where the epidemic has raged for years. Nevertheless, even there, he notes, “You could still have ash on the landscape — you might not have it at the same proportion and at the same frequency that we see it now, but it would still be there.”
Back in the city where the infestation first began, Rob Davies, has momentarily forgotten all about ash. A red oak tree next to a borer-infected ash sapling in Devonwood has caught the Essex Region Conservation Authority forester’s attention. Oak wilt, a fungal disease that has been killing oak trees in the United States, is now only a few kilometres away, having reached Belle Isle Park in the Detroit River. The tree, which had seemed all right in spring, is dead.
Oak wilt may not be responsible for the tree’s sudden turn for the worse. But Davies is not about to take any chances, with the next possible invader of Ontario’s forests right on Windsor’s doorstep. As he returns to the conservation area’s parking lot, he’s already making plans to call in an expert from the Ministry of Natural Resources and Forestry.
This is one in a series of stories about issues affecting southwestern Ontario. It's brought to you with the assistance of faculty and students from Western University’s Faculty of Information and Media Studies.
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