By Jason McLean
Brenda Burke stands pointing up to the branches of a crabapple tree just starting to sprout some buds. With its greenery poking through for another year, the tree looks happy enough, but then Burke zeroes in on some off-white patches periodically dotting the bark — egg masses, it turns out.
“Last year, they hadn’t made it this far into the neighbourhood, but as you can see they’ve arrived,” Burke said.
The ‘they’ in question are Gypsy moths, an invasive species that, last summer, reached outbreak proportions across parts of Eastern Ontario and has, unfortunately, made its presence felt in Old Ottawa East.
Particularly hard hit are trees in the northern corner of the community on the provincial Ministry of Transportation land adjacent to the Highway 417 on-ramp and in the area surrounding Greenfield Court at the ends of Montcalm and Havelock streets. In larval form, the Gypsy Moth is a spiky-haired caterpillar with blue and red spots along its back that can eat about a square metre of leaf material over the course of its lifespan.
Amazingly, Gypsy Moth caterpillars can strip a tree bare within a few days. The outbreak in Ontario is now being called the worst in decades, and while Ottawa’s municipal foresters are continuing to monitor the situation, Burke and her neighbours are bracing for the worst, having last summer endured both COVID-19 and an onslaught of caterpillars, their feces and dive-bombing Gypsy moths.
“We didn’t know what we were dealing with,” Burke said. “There were tonnes of caterpillars coming down in webs. One of my neighbours said it felt like the apocalypse.”
“It reached a point where you couldn’t sit outside because there’d be caterpillars dropping all around you. Some neighbours put up screen tents on their decks but, honestly, I think I was out for one evening all last summer,” she said.
Arriving in New England in 1869 as part of a failed silkworm breeding program, the Gypsy Moth is now established in Ontario, Quebec and the Maritimes. Outbreaks tend to happen every seven to ten years, with populations typically dying back after a couple of years due to predation, parasites and other factors.
“Since they first arrived, Gypsy Moths have been migrating northwards, now due to climate change and shifting ranges,” says Adam Oliver Brown, Assistant Professor with the Department of Biology at the University of Ottawa. “Their populations go through cycles, and they can get really bad in some years, largely because they don’t have natural predators or diseases over here.”
Brown says outbreaks can be treated with insecticide, and cities have done aerial sprays of a bacteria toxin specific to moths called Btk or Bacillus thuringiensis kurstaki.“But spraying is frankly a PR nightmare,” Brown said. “People really don’t like the idea of being sprayed with bacteria.”
There are more hands-on approaches such as scraping the moth’s egg masses from infected trees and other locations — moth eggs can appear on brick walls, fences and other surfaces — and trees can be wrapped in burlap around their trunks to catch caterpillars heading for the ground. There are bottle traps, too, for the adult moths.
But none of these methods are 100-percent effective, nor are they a lot of fun.
“We did the egg scraping last year and the bottle method,” says Burke. “You have to submerge the eggs in soapy water for two days, and with the bottle, you hang it from a tree, and they crawl inside, and then you have to scoop them all up, which is a gross job.”
So far, the City of Ottawa has stuck to a wait-and-see approach, having released a statement last month on its monitoring to date and how residents can try to tackle the pests on their own. City Forester Jason Pollard says the City completed surveys over the winter to estimate populations for this year.
“Locally, Ottawa experienced elevated populations of Gypsy Moth in 2020 which have been assessed to be minor. Although the moth can cause significant defoliation, it is only repeated years of defoliation in trees and forests that generally impact tree health,” Pollard said in an email.
“It’s also important to note that this insect pest has a periodic outbreak cycle, so we can expect elevated populations followed by population collapse typically after two to three years,” Pollard said.
For Burke, who is treasurer for her condo board, and who is helping to coordinate efforts this year in spraying and burlap-wrapping trees, she said she understands the City’s perspective but is worried, nonetheless.
“Already, some of the trees are eaten through and the caterpillars keep growing,” Burke said. “We know we have to act and do what we can to reduce their numbers.”
