Outbreak of forest tent caterpillars should last about 6 weeks

Experts say that in northeastern Ontario, the outbreak of forest tent caterpillars this year should last about six weeks.

They’re creepy, they’re crawly and they seem to be everywhere. Forest tent caterpillars are cropping up in large numbers across northeastern Ontario.

Experts say we’re in an outbreak.

“It’s not as severe as it has been in the past,” said Dan Rowlinson, the provincial forest health field coordinator with the Ministry of Natural Resources.

“They’re just in the tiny larval stage right now. So, they’re just starting to feed on the aspen and the poplar trees. But they’ll proceed through the summer and then we’ll see more defoliation. I don’t think it’s going to be as significant as it was last year.”

MNR monitoring shows eastern tent caterpillars are a problem, but Rowlinson said they’re not as widespread as the forest tent species, also known as armyworms. Those are the ones experiencing the population boom.

“We’re looking at about six weeks,” said Alexandra Binns, Science North’s animal care technician, who said the area is on the upswing of a 10-year cycle.

The last big outbreak was in 2018.

“Generally, once the young caterpillars emerge in early springtime, they can only really eat soft or freshly grown leaves,” Binns said.

“Because they can only eat those things, they eat them for about six weeks. That’s the fresh start of spring. And then they’ll start to cocoon and pupate from there.”

Later in the summer, these pests will transform into moths.

Despite their annoyance, experts agree that forest tent caterpillars are important to the ecological landscape.

“They are more nutrients for birds and things like that,” said David Dutkiewicz, an entomology technician with the Invasive Species Centre.

“Mice, rodents, but also birds and migratory birds, it’s a quick and easy meal for them. And so as much as we might hate them, they are important to the environment.”

Dutkiewicz said picking the forest tent caterpillars off trees and other greenery or wrapping tinfoil around the base of the tree. He said spraying them with soapy water will also work, but doing it too often could harm the tree’s protective wax coating.

In case children pick one up or they fall from trees onto unsuspecting folks below, it’s important to remember the caterpillars aren’t harmful to humans, unless there is an allergy to the critters’ hairs.

Mostly, they’re just annoying and gross.