Tent caterpillars occupy a tree in Aroostook County. Credit: Courtesy of Maine Department of Agriculture, Conservation and Forestry

FORT KENT, Maine — People who lived in northern Aroostook County during the early 1980s remember the invasion of forest tent caterpillars that swarmed the area in the millions. Memories of roads made slick with crushed caterpillars and the stench when the insects died en masse in large numbers still linger.

That’s why St. John Valley residents who have noticed more tent caterpillars than usual creeping into the neighborhoods are a little nervous.

With woods covering nearly 90 percent of Maine and the forest products industry contributing more than $8 billion to the state’s economy, an insect that can strip deciduous trees of leaves is a formidable threat.

The caterpillars were first seen in eastern Quebec and by 1979 were found in approximately 20,000 acres of St. John Valley woodlands. In 1980, they had spread into northern Maine, infesting 120,000 acres and reaching their peak at around 800,000 acres in 1982, according to Maine Forest Service entomologist Dave Struble in a 2018 interview.

“My brother got married in late May [1981] and it was awful,” Leland Roy of Fort Kent said. “Roads were gross with so many caterpillars being run over and you could hear them pop under the tires.”

Credit: Courtesy of Maine Department of Agriculture, Conservation and Forestry

Brian Bouley describes the situation in Grand Isle at the time as “apocalyptic.”

“I remember trees stripped of their leaves, cars literally slipping on the road at Mt. Carmel, my Dad burning them in the trees with a torch and the moths afterward,” Bouley said. “I remember everyone wrapping their tree trunks in foil or plastic to keep them away.

“I saw bunches of them in branches last week; they’re coming,” he said.

Tent caterpillars occupy a tree. Credit: Maine Department of Agriculture, Conservation and Forestry

Bouley is not entirely wrong, according to Allison Kanoti, state entomologist, director of Forest Health and Monitoring, Maine Forest Service.

This is the second year northern Maine has experienced higher populations of forest tent caterpillars, scientific name Malacosoma disstria, in recent times, Kanoti said.

The forest tent caterpillars are not toxic to humans, but they can kill trees if they defoliate the same ones multiple years in a row.

The caterpillars have stripped leaves from patches of aspen and other hardwoods in Caribou, Fort Kent, Frenchville, Madawaska, New Canada, Van Buren, Wallagrass, Winterville Plantation and Woodland.

Last year, the fuzzy insects defoliated almost 240 acres of trees in Fort Kent and Frenchville alone.

A similar situation occurred in Blue Hill four years ago when forest tent caterpillars destroyed a canopy of oak trees, and were so numerous that state officials posted signs in the town warning of slippery roadways.

Such proliferations of forest tent caterpillars generally last only a couple of years, Kanoti said. The caterpillars’ feeding this year should wrap up sometime around Father’s Day weekend, she said.

Roy said many efforts were made by locals to kill the caterpillars back in the 1980s.

“In the end, nothing really worked well. They just needed to complete their cycle,” Roy said.

Those who observe tree damage from forest tent caterpillars — which will be determined by the trees having leaf loss but stems remaining on them — in northern Aroostook County are asked to report it to the Maine Forest Service through an online form, or at foresthealth@maine.gov or 207-287-2431.