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- File: Oliver Parini
- Spongy moth caterpillar
For the past two summers, spongy moth caterpillars wreaked havoc in pockets of Vermont — stripping oak and maple trees, swinging from silken threads, and leaving behind a mess of excrement and chewed-up leaves.
In 2021, the hairy, spotted creatures defoliated 50,000 acres of forest. And in 2022, they ate their way through 40,000 acres. But this year, the insidious insects — formerly known as gypsy moths — haven't been spotted yet. Are we finally in the clear?
It's too early in the season to say for sure, but Josh Halman, forest health program lead for the Vermont Department of Forests, Parks and Recreation, is cautiously optimistic. A week into June, Halman said his department hadn't received any citizen reports of spongy moth activity. In 2021 and 2022, it started getting calls about the caterpillars in mid-May, he said.
Halman attributed the decline to several factors. When the spongy moth outbreak started two years ago, Vermont was in the middle of a deep drought. The water-loving fungus that typically kills the caterpillar larvae couldn't proliferate. But in the past year, there's been ample moisture.
Further, Halman said, caterpillar outbreaks typically follow a bell curve — with the situation reaching a peak of awfulness, then crashing. Right now, we're likely at the tail end of that curve.
Last fall, Halman and his fellow foresters surveyed nine plots around the state looking for spongy moth egg masses — something the forest department has been doing for the past 30 years — and found significantly fewer than they had in 2020 and 2021.
Later this month, the foresters will take to the air in a Cessna four-seater piloted by the Vermont Wing of the Civil Air Patrol to quantify what kind of impact, if any, the caterpillars are having. They'll also be able to assess whether the caterpillars did any permanent damage to Vermont's trees in 2021 and 2022.
Historically, spongy moth outbreaks occur every 15 years or so, Halman noted. If that pattern holds, Vermonters can breathe a sigh of relief — until 2036, at least.