Invasion of the creepy-crawlies: Southern Ontario residents battling plague of caterpillars

After struggling for years to control the invasive Asian longhorned beetle, the Canadian Food Inspection Agency has announced the tree-killing insect has finally been eradicated in Canada.

Infestations come once every decade or so

In front of Caledon's town hall, Gypsy Moth caterpillars cluster in the crotch of a maple tree. Biologist and invasive species expert Bryana McLoughlin says the caterpillars come down from trees' canopies to escape the afternoon heat. (Mike Smee/CBC)

After struggling for years to control the invasive Asian longhorned beetle, the Canadian Food Inspection Agency has announced the tree-killing insect has finally been eradicated in Canada.

But as that struggle ends, another one is being waged in several Ontario communities, against a different invasive insect.

Hordes of Gypsy Moth caterpillars are being reported in Eastern Ontario, Bancroft, Kitchener-Waterloo, Guelph, Vaughan and Caledon.

"It becomes noticeable when people are sitting on their back patio and there are insects plopping into their drinks," said Peter Wynnyczuk, a forestry technician and president of P and A Urban Forestry Consulting in Toronto.

"They're very aggressive when the populations are high ... They'll start to eat anything that's green ... including lawns, with the exception of poison ivy."

Invasive species expert Bryana McLaughlin, of Credit Valley Conservation, examines a group of caterpillars clustered on one of the trees in front of Caledon's town hall. (Mark Bochsler/CBC)

Caledon is one of the infestation hotspots. At the Credit Valley Conservation Authority there, invasive species expert Bryana McLaughlin said Gypsy Moth go through steep population spurts every decade or so, and the Caledon area happens to be in the midst of one now.

"We have been getting a lot of calls; people are really concerned especially in this area," she said.

"The trees are noticeably being eaten and a lot of them have lost their leaves completely ... but generally as long as they're not being completely defoliated for more than two years they can usually pull through."

A statement from Caledon's town council warns homeowners that the municipality won't intervene if a caterpillar breakout happens on private property.

Caledon resident Sharyn Holloway, with the burlap band she has strapped around the maple tree in front of her house. It's had limited effect — the tree still contained caterpillars last week. (Mike Smee/CBC)

Several residents there say they've been trying — in vain — to stem the Gypsy Moth caterpillar tide.

Wayne McTaggart taped a belt of duct tape, sticky side out, around his trees, on the advice of an arbourist.

He's also been spending time trying, unsuccessfully, to clean the sidewalk in front of his Caledon home. It's been stained dark brown with excrement from the caterpillars that are swarming over one of his trees.

His neighbour, Sharyn Holloway, has also been trying, just as unsuccessfully, to control the infestation on her property by using a solution commonly suggested by experts: She wrapped a belt of burlap at chest height around her maple tree. In the heat of the afternoon, the caterpillars seek shelter there, allowing her to spray them down with soapy water, which supposedly kills them.

A closer look at one leaf being eaten. (Mark Bochsler/Julia Whalen/CBC)

"They're terrible," she said. "And it's what they drop on the driveway — that's the problem.

"I've lived here for 14 years, and this is the first time I've had it, so..."

McLaughlin suggests hunting for the nests — beige, fuzzy areas about the size of a toonie that appear on the sides of trees and houses — and scraping them off into soapy water.

Other than that, she suggests patience may be the best strategy.

This young oak tree, on Old Church Road in Caledon, has been stripped clean by Gypsy Moth caterpillars. (Mark Bochsler/CBC)

"So at this point there's not a whole lot to do, other than trying to remove the mature caterpillars from your trees," she said. 

In another month or so, the larvae will pupate into adult Gypsy Moths.

At Caledon's town hall, Mayor Allan Thompson wouldn't speak with CBC Toronto about the problem. But regional councillor Johanna Downey said the local infestation was discussed by councillors at their meeting last Tuesday.

She said council has asked staff to come up with a strategy to fight the Gypsy Moths, and some suggestions should be presented to council in a couple of weeks.

Another Caledon councillor, Lynn Kiernan, appeared to take a stoic approach to the problem.

"Many, many areas in Ontario are facing some problems with Gypsy Moths this year. Caledon just happens to be one of them," she said.

"And you know, nature tells us that these are cyclical, and this too shall pass."


Michael Smee

Reporter, CBC Toronto

Michael Smee has worked in print, radio, TV and online journalism for many years. You can reach him at