As caterpillars eat N.B. maple leaves, syrup producers consider insecticide solution

Forest tent caterpillars are shown in a forest in northwestern New Brunswick in a July, 2024 handout photo. THE CANADIAN PRESS/HO-Frederick Dion/New Brunswick Maple Syrup Association

GRAND FALLS, N.B. -

New Brunswick's maple syrup industry is considering using an insecticide to kill off forest tent caterpillars that have chewed through a portion of the province's northwestern woodlands this summer.

The province's Department of Natural Resources is estimating that green, fuzzy caterpillars have caused the defoliation of about 120 square kilometres of forests on or near maple syrup farms.

Producers are fearful the result will be unhealthy trees -- and lower production of syrup in next spring's runoff, Frederick Dion, president of the New Brunswick Maple Syrup Association, said in an interview earlier this week.

"You walk through the forest and you hear the sounds of millions of those caterpillars eating the leaves and it's disastrous when you see it," said Dion, who in addition to his volunteer role at the association runs his own maple syrup operation.

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He said that during most summers the maple trees form a heavy, green canopy -- but the most recent infestation has partially denuded trees, allowing heat to beat down on the forest floor.

"If (next year) we have a big drought combined with the insects, we're going to have a major problem," Dion said.

According to figures compiled by the association, producers generate about three million litres of syrup annually -- a figure Dion estimates is an increase of about 50 per cent in a decade. Syrup from New Brunswick represents about five per cent of international production, which remains dominated by Quebec.

However, there's a possibility that the caterpillars may pose a long-term challenge to the nascent East Coast industry, as climate change causes insects to arrive on the scene earlier in the year, said Anne-Sophie Caron, an entomologist who recently completed her doctorate on the caterpillars at Concordia University in Montreal.

"The (caterpillars) are coming just as the trees are budding .... So, they are able to eat the leaves as soon as the leaves come out," she said in an interview Friday.

Glenn Somers, a maple syrup producer in the Saint-Quentin area, about 300 kilometres north of Fredericton, said the insecticide option is being considered "because we're scared about losing too many of the maple (trees)."

Dion estimates 30 to 40 producers of syrup have been hit with some level of infestation and says the association is studying the potential spraying of the biological insecticide BTK next spring to try to prevent a recurrence. That insecticide would be sprayed on maple leaves and -- after the BTK is ingested by the caterpillar -- would kill the insect without damaging the wider forest ecology, he said.

Maple syrup producers would need to pay for the insecticide, he added, while the provincial government has to approve its use.

However, the use of the spray may have to become a regular event to be effective, said Caron. "It's something you would have to do every year," she said. "But if it reduces the population enough, you'd have less reproduction."

Beverly Gingras, director of the Conservation Council of New Brunswick, said in an email that BTK affects all moth and butterfly larvae species, "so if it is used, it should be done carefully and only in targeted areas."

"If it will be used, it's better to spray early to control the outbreak and to minimize use. We also suggest that those involved work closely with First Nations and local communities to decide if, where and when to spray," she wrote.

Gingras noted that tent caterpillars are native to New Brunswick, and their outbreaks occur in cycles of about 10 to 12 years as part of the natural cycle of the forest.

"What we might be witnessing now is the impact of climate change on the maple syrup industry. With more extreme weather from climate change -- like prolonged droughts, false springs, late frosts and extreme heat -- maple trees may become more vulnerable to native and invasive pest species," she added.

This report by The Canadian Press was first published July 26, 2024.

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