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What you need to know about COVID-19: August 14, 2020
Maybe deep in its genes it still yearns for the long sleepy summers of its heartland in the Mississippi Valley.
Late to bud and early to turn auburn and pack it in for a long winter’s nap, white ash could be called lazy.
Or charmed – as always these things depend on who is making the value judgements.
Still broke from college and with an old farmhouse on a half acre he intended to fill with trees, Gary Saunders found some ash saplings a half century ago on a neighbour’s property in Clifton, Colchester County.
As the trained forester had expected, they grew fast.
While he has grown older, with a life expectancy of up to two centuries they are not even yet middle aged.
It was on his favourite – the one outside his workshop window that alternately gave cool shade in summer and cradled cold winter suns- that he noticed it first.
It began dropping its leaves early, even by the standard of the sleepy ash, then died.
“At that point I didn’t get it,” said Saunders who spent much of his career writing and editing for the Department of Lands and Forests, most recently producing a memoir/education book on the Acadian Forest titled My Life with Trees.
“Then the one down the road got it. Ash blight. It’s a fungus. The leaves just curled over and had these yellow, furry edges.”
Hymenoscyphus fraxineus is a fungus of east Asian origin that has devastated the European Ash trees of the United Kingdom.
Host of pests
And it’s the lesser of the worries faced by our own white, red and black ash in Nova Scotia.
We’d probably call emerald ash borer pretty in its green armour if it weren’t about to wipe out such an elegant member of our Acadian forest.
Likely transported in wooden packing crates from its home in China and the Russian near east, the insect has woefully few natural predators in North America. Since its discovery just south of Detroit in 2002 it has wiped out over 30 million ash trees in Michigan – which would be nearly all of them.
It’s just one of a host of pests from around the world that due to the increased mobility of both humans and the stuff we buy from each other, are now posing an existential threat to the Acadian forest as we know it.
“Like bacteria breeding several times a minute, the fungi can produce improved variations of themselves much faster than we can produce more (resistant) trees,” Saunders.
“I don’t hold out much hope. The time scales are against us. We have the same problem – corona (virus) and SARS – they’re chasing us too.”
Native to Asia, the hemlock wooly adelgid is capable of taking down those lords of the forest, the towering Eastern hemlock. The tiny aphid-like insect whose eggsacks resemble cotton balls at the base of needles has marched across the continent since first being identified in British Columbia in 1920. The Canadian Food Inspection Agency confirmed its presence in Shelburne, Yarmouth and Digby counties in 2017.
Then there’s the beech leaf-mining weevil.
“It’s well established now, killing the beech that had survived beech bark disease,” said Jon Sweeney, a research scientist with the Canadian Forest Service.
Prior to 1897 the long-lived American Beech, which as a nut-bearing tree was a boon for wildlife and produced lumber harder than sugar maple, was estimated to compose 60 per cent of Nova Scotia’s hardwood forests. But then Queen Victoria sent two European beeches to the public gardens in Halifax in celebration of her half-century on the throne. They were, no doubt unintentional, hosts to a sapsucking aphid that in concert with a fungus have since wiped nearly all the beeches in Eastern North America and left those that have survived as gnarled and pitiful vestiges of what was once a great and noble tree.
Then there was of course Dutch elm disease, cursed by many of us for having robbed our downtowns and river valleys of the American elm’s stately companionship. It arrived on our coast via Europe from Asia in the 1940s.
“More will come,” said Saunders
The world continues to shrink, not just for us, but also for the parasitic insects and fungi that hitch a ride in packing crates and on the bottoms of our Birkenstocks. Pests that our trees have not evolved alongside and therefore have limited resistance to.
This province’s exports to China have ballooned from $46 million a decade ago to just under a billion dollars. All those planes and ships travel in two directions.
Earlier week those on the front lines of the fight for our forests filled the Halifax Marriott Harbourfront Hotel for the SERG International conference.
The scientists, foresters, government and industry folk from around the western hemisphere breathed the atmosphere of conference rooms filled with those whose interest in trees matched their own as if it were a purer form of oxygen.
We look at everything through the viewpoint of our own lifetime. . . But you have to transcend that when thinking about trees.”
- Tree enthusiast Henri Steeghs
Sweeney presented on his plan to place traps in the canopy of ash trees around Bedford this spring that lure emerald ash borers in with a pheromone, expose them to a naturally occurring soil fungus then allow them to escape. The insects then pass the fungus along to others of their own kind before dying from it a few days later.
“It has the potential to slow the spread but it won’t stop it,” said Sweeney.
“It’s one of the tools in the toolbox.”
It is biological warfare.
The advantage to Sweeney’s traps is that the fungus they use, beauveria bassiana, already exists in the environment. The borer just doesn’t usually get exposed to the soil-based fungus because it spends its larval stage in the ash tree itself then goes flying around to feed and mate.
Another tool being used by Natural Resources Canada since 2013 has been the introduction of three different varieties of a parasitic wasp from Asia that prey on the Emerald ash borer.
The first release of these parasitic wasps in the Maritimes was done last year just south of Edmunston, New Brunswick.
“You are releasing a non-native species to control a non-native species,” said Sweeney who acknowledged humans have made some “very bad mistakes” when trying this.
He added that two panels of Canadian scientists had to be convinced there was a very low risk to native species by the released Asian wasps.
So far this hasn’t been tried for the outbreak of emerald ash borer near Bedford, which continues to expand slowly at a rate of about half a kilometre per year.
Like most outbreaks of invasive species, the dread is that the battle’s loss is inevitable as soon as it begins.
At a kitchen table in Antigonish County, Henri Steeghs was thinking about time.
“We look at everything through the viewpoint of our own lifetimes,” said Steeghs, a lifelong tree enthusiast who formerly owned Pleasant Valley Nurseries in Antigonish with his wife Phyllis.
“It's the warmth of that that keeps us going. But you have to transcend that when thinking about trees.”
The oldest eastern hemlocks found would have been saplings when Christopher Columbus set off from Spain a half-millennia ago.
In one sense that puts them at a disadvantage in the evolutionary arms race. Think back to Saunders’ comment about bacteria reproducing several times a minute and how quickly new varieties pop up.
But a tree is a battleship.
Its bark would be its armour but like any ship its true strength would be in the inner workings of the crew. That in this metaphor would be its genes and the long memory they carry of predators bested and environments survived by its ancestors.
We too are survivors of plague upon plague upon plague that have hammered back the human population over its evolution. We, like trees, carry the genetic memory of survivors.
The “best bit of good news” Sweeney could offer was that one per cent of the ash trees in Michigan have survived and appear to be resistant.
Like the towering American beech surrounded by its sadly gnarled and infected cousins Steeghs found in Monastery, Antigonish County.
Given thousands of years the descendents of the survivors with genetic resistance to pests and pestilence have the potential to cover our landscape once again, as they have done in the past.
Steeghs just isn’t inclined to wait that long.
“I feel a bit foolish even talking about it,” he admits of his project. “It’s such a long shot.”
The senior citizen has been laddering disease-resistant American beech each recent February (the best season for the task) and climbing up to snip cuttings of new growth.
He then grafts clones of the trees.
Something that he had initially thought would be easy enough as he’d spent a lifetime grafting various species for his nursery.
Not so, as it turned out.
Beech is so hard he needed to order a special tool from New Zealand.
As well, he has to apply heat and mist to the graft union to encourage healing while keeping the rest of the saplings cool.
Toiling away alone with numerous disappointments he’s managed to create over 40 disease-resistant American beech clones. The most effective way to help the American beech along would be to create a colony far enough away – at least 10 kilometre – from any of its genetically non-resistent fellows. This would allow the trees to pollinate one another and sire saplings with strong genetic resistance.
Instead of millennia, within 40 or 50 years seed could be collecting to raise saplings that are planted en masse around Atlantic Canada.
“Then the non-resistant trees would be the Neanderthals,” said Steeghs.
Though he’s a healthy man, Steeghs isn’t banking on having 50 years to see his project through.
He also doesn’t have the resources to take it much further than he already has.
It would require a government or academic agency with skilled people and resources to take over.
“Whatever I have left, I want to pass it on,” said Steeghs.
Back in his home on the Bay of Fundy coast surrounded by the dying ash trees he planted as a young man, Saunders too holds out hope for a forest that he knows he won’t live to see.
“On their timescale, they have lots of time,” said Saunders of trees.