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See infestation that could plague Canadian homes this spring

Leeanna McLean
Digital Reporter

Monday, February 26, 2018, 5:28 PM - While most people are looking forward to warmer temperatures and spring blossom, Saskatoon resident Tammi Hanowski fears her home will once again be plagued by caterpillars.

Hanowski was one of several Canadians who experienced a near-biblical swarm of forest tent caterpillars last May.

"It was probably a week of this massive infestation," the Saskatchewanian told The Weather Network. "We're talking probably tens of thousands of caterpillars that were just everywhere."

Visit our Complete Guide to Spring 2018 for an in depth look at the Spring Forecast, tips to plan for it and much more.

The forest tent caterpillar is found across Canada and every province can experience an outbreak.

Image courtesy: Joshua Mayer -- Creative Commons

The amount of time in between outbreaks is dependent on what province you live in, according to Dr. Amanda Roe, research scientist with the Great Lakes Forestry Centre.

In Ontario for instance, an infestation can occur every eight to 10 years, and can last two to three years.

"You can actually notice they look like little tar balls all the way around the branch in the forests. Those are the egg baskets that are waiting to emerge in the spring and they all come out together," said Dr. Roe

The insect has historically caused extensive defoliation of trembling aspen, oak, ash, maple and white birch trees.

About 150,000 hectares of land was defoliated by forest tent caterpillars in 2009, according to Natural Resources Canada.

Scientists have records of tent caterpillars in Ontario and Quebec dating back to the 1930s. Defoliation was at it's most intense during the period of 1951 and 1954, the agency reports. 

"They specialize on the new, fresh leaves. You know, that first big green flush of leaves that you see on birch and maple trees. That real first hint of spring, that's when they are getting ready to feed," said Dr. Roe.

WATCH a caterpillar transform into a butterfly before your very eyes

Not only do they feast together, but they move together as one.

"People have seen them going across the road and you can't see the lines of the road anymore. It's just a shimmering mass of caterpillars all moving from one part of the forest to the next part of the forest."

Outbreak cycles are also dependent on local weather conditions.

"When they're in their eggs baskets they can withstand winter temperatures. They don't have a lot of protection, they are just hanging on the trees and not hiding under the snow like a lot of other insects might," said Dr. Roe. "But, once they emerge in the spring, certain conditions can impact them. A late spring frost can really impact them. It can result in really high levels of mortality."

Since tent caterpillars are native to North America, insect parasites and natural predators like birds and rodents help to control the population.

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"The idea of control becomes an interesting question because when you're talking within the forest, this is actually a natural part of the ecosystem and our forests are adapted to outbreaks," said Dr. Roe. "It's much like fire. It's a natural disturbance and it's important to allow those natural disturbances to go through the forest because it keeps our forests healthy."

In Hanowski's case, she used a vacuum to help control the infestation, but she quickly learned it was not enough.

"We kind of vaccuumed them up with the shop vac, but then an hour later there would just be double the amount," Hanowski said. "There was one corner of our house where they just seemed to want to migrate to. There was a video of me kind of sweeping through them with my boot, and honestly it was probably a good six inches deep."

Eventually the family contacted Poulin's Pest Control Services. The company sprayed the Hanowski property for about five hours with an insecticide.

"As spring is coming we're just like ugh, I hope this doesn't happen again," said the Saskatoon resident. "I think probably in the next month or something we'll probably take a walk out to the trees and see if there's anything that we need to do. We don't want to think about it, but I think we kind of have to."

WATCH BELOW: Canada's National Spring Forecast 2018

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