5 things you may not know about northern Ontario's caterpillar infestation

Millions of caterpillars are annoying and grossing out people across the north this spring, while stripping their trees bare. But scientists and government officials say they are more nuisance than natural disaster.

Tent caterpillar population swells every 10 years

A tent caterpillar climbs a tree in Memorial Park in downtown Sudbury, where several trees have been stripped of all their leaves. (Erik White/CBC )

Northern Ontario is once again crawling with tent caterpillars.

They are munching their way across the region and leaving few leaves on poplar and birch trees, which are their favourites.

While most northerners are annoyed or grossed out by the infestation, Jennifer Babin-Fenske and her kids in Sudbury celebrate the onslaught.

"We go out in the backyard and they pick out their caterpillar and name it and then release it and it's a one month pet and it's wonderful," says the entomologist, who is also coordinator of the City of Greater Sudbury's Earth Care program.

Jennifer Babin-Fenske is an entomologist and the coordinator of Earth Care at the City of Greater Sudbury. (Erik White/CBC )

Dan Rowlindson, the Sault Ste. Marie-based forest health coordinator for the Ministry of Natural Resources and Forestry, says the caterpillars will chew up about 1.5 million hectares of forest this spring.

He says the caterpillar outbreaks comes every 10 years and that surge lasts for three to five years.

"You can almost set your watch by an outbreak cycle," says Rowlindson.

He says the caterpillars can cause real problems for the human population of northern Ontario, but says because this is a native species to our area and a natural process, there is no need to try to control them.

"Mother Nature knows what she's doing out there," Rowlindson says.

Only eastern tent caterpillars nest in tents like this one, while the ones behind the outbreak, the forest tent caterpillar lay their eggs in smaller sacks. (Erik White/CBC)

5 things you might have known about tent caterpillars

1. The tent caterpillars behind the outbreak don't actually make tents

There are two kinds of tent caterpillars found in northern Ontario. The eastern tent caterpillar has a white stripe, lays its eggs in tents and doesn't go through dramatic population increases. The forest tent caterpillar lays its eggs in small sacks, has white spots and is the critter that comes by the millions every 10 years or so.

An eastern tent caterpillar with characteristic white stripe. (Erik White/CBC )
A forest tent caterpillar with white spots. (Erik White/CBC)

2. Sudbury is a hot spot for infestations of caterpillars and other insects

Babin-Fenske says a study in the early 1990s showed that outbreaks of tent caterpillars and other bugs lasts longer in Sudbury than other parts of Ontario, likely due to the historically tough growing conditions caused by decades of mining pollution.

3. It looks bad, but the bare forests are actually good for the environment

Rowlindson says the stripping of foliage by tent caterpillars is part of nature's regular cycle. The thinning out of the forest canopy allows light to reach smaller plants, the caterpillars themselves are a good food source for birds and other animals and when they die (and defecate) they fertilize the forest floor.

Tent caterpillars are expected to chew up about 1.5 million hectares of Ontario forest this spring. (Erik White/CBC)

4. The worms go marching

Tent caterpillars are also known as army worms, because they will actually march in large groups and once they've defoliated an area, they will move to another part of the forest. This sometimes leads to northern Ontario roads being closed.

5. The caterpillar invasion is not a new thing

While we might think of insect invasions as a new thing that comes with the global village, tent caterpillars are native to Ontario and have been breaking out every 10 years for centuries. A search of Sudbury newspaper archives, shows a story back in June 1936 about how trains were delayed by slippery rails and one from 1988 about how masses of caterpillars were shorting out hydro lines in the Sudbury area.

A story from the Sudbury Star in June 1936 about a tent caterpillar infestation. (Greater Sudbury Public Library )