As cities panic over a gypsy moth invasion, Ontario's Pinery park tells visitors to 'roll with it'

Many Canadian communities panic over gypsy moth invasions that have left suburban trees wrapped in duct tape and burlap. Ontario's Pinery Provincial Park aims to educate visitors about the pests, including how to best tolerate them and what they leave behind.

Gypsy moths found mainly in Ontario, Quebec, Maritimes

'To many people, the trees look like they've died'

1 year ago
Duration 2:37
Alistair MacKenzie with Ontario Parks says he's not too worried about the LDD moth caterpillars ravaging one of the province's rarest ecosystems.

There are so many gypsy moth caterpillars in the canopy above the Heritage hiking trail in Pinery Provincial Park, you can actually hear them. 

"Yeah, there's sort of that little patter in the background," said Alistair MacKenzie, a manager with Ontario Parks who's been working at the Pinery near Grand Bend for two decades. 

In fact, that "patter" sounds a lot like rain. Except, it's not. It's something scientists call "frass."

"Scientists have lots of different names for scat," MacKenzie said. 

According to the federal government, the gypsy moth is found mainly in Ontario, Quebec and the Maritime provinces.

In southern Ontario, communities panic over a gypsy moth invasion that's left hundreds of suburban trees wrapped in duct tape and burlap. Mississauga, for one, monitors and controls gypsy moth populations, identifies areas where there are high numbers, and treats city-owned trees, including scraping egg masses off infected trees, where they may also hang traps to catch male moths and prevent them from mating.

The widespread damage from gypsy moth caterpillars is apparent, even to the untrained eye, in Pinery Provincial Park on Lake Huron near Grand Bend, Ont. This ragged-looking oak tree has lost many of its leaves. (Colin Butler/CBC News)

However, MacKenzie, who's in charge of protecting one of the rarest and most fragile ecosystems in Ontario, is a lot more relaxed about the situation.

"To be honest, at present, we're really just observing," he said. "We're not anticipating any long-term effects from this."

It seems counterintuitive, especially when cities such as nearby London, Ont., have called community meetings about the insects and used airplanes to get rid of them, while media coverage about the caterpillars uses words and phrases like "dreaded," "tree killer" and "voracious threat."

"I think it's a sign that people are just getting a little bit removed from nature," MacKenzie said. 

"We know this species from decades of research by experts is one that goes through boom and bust cycles. It's likely we'll have this outbreak for three to five years and then they'll diminish and become another background species in the forest. 

"There's no intention for Ontario Parks to do any spraying or any treatments in any of our properties this year," he said.

"It's important that when we talk about invasive species, we weigh the impact from the species itself and the control mechanisms that might be available."

Ontario Parks to let nature take its course

Instead, MacKenzie said, in a forest, it makes more sense to let nature take its course. While the damage borne by a gypsy moth caterpillar may be ugly, it's unlikely the critters will actually kill their hosts. 

Burlap or duct tape can be seen wrapped around trees in many suburban neighbourhoods across southern Ontario to defend trees against gypsy moth caterpillars. (Colin Butler/CBC News)

"It doesn't make a lot of sense for them."

He notes it is possible, but usually because something else, such as drought, fungus or some other insect is also affecting the tree's health. It's not in a gypsy moth caterpillar's interest to actually finish off its meal. 

"If they eat themselves out of a house and home, their next generation won't necessarily survive. So by nature, they move across the landscape and go through these cycles of abundance and decline."

The last time the Pinery went through a major gypsy moth caterpillar infestation was in 1994. This time around, the park is in its third year of an infestation that can last anywhere from three to seven years.

Last year, the insects consumed so many leaves that much of the canopy along nearby Highway 21 and the park's entrance looked ragged and bare, giving visitors to the park an eye-opening first impression of what, under normal circumstances, is supposed to be one of Ontario's ecological jewels.

Caterpillars may be around till late June, early July

"To many people, it appears the trees have all died. So there are questions about, 'Was it a fire?' 'Is there some other stressor going on?' Thankfully most trees, especially the oak trees here, have a lot resilience."

A gypsy moth caterpillar dines out on leaves in the understory of a Carolinian forest in Pinery Provincial Park. (Colin Butler/CBC News)

It's one of the lessons human beings often fail to learn: if we just stay out of the way, nature often works things out on its own. It's why the Pinery is trying to educate visitors about the pests, and how to best tolerate them and what they leave behind.

"We anticipate the worst of the sort of inconvenience of the caterpillars and their frass falling from the canopy will be over by the end of June or early July," said MacKenzie.

"We ask people to just sort of roll with it. It's one of those stressors that will ultimately make this park more diverse. Even if some trees do succumb, it will open up sunny opening in the forest that will lead to more species and other species growing." 

MacKenzie said the park is asking visitors to consider wearing long-sleeved shirts and hats in case caterpillars drop down from the trees on silken threads, emphasizing there's no immediate health risks from the insects. 


Colin Butler


Colin Butler covers the environment, real estate, justice as well as urban and rural affairs for CBC News in London, Ont. He is a veteran journalist with 20 years' experience in print, radio and television in seven Canadian cities. You can email him at