Predicting gypsy moth caterpillar’s cycle an inexact science

Published: Jul. 9, 2021 at 3:38 PM EDT
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BURLINGTON, Vt. (WCAX) - Gypsy moth caterpillars continue to cause devastation to trees across the region but experts say it’s still not clear what their numbers mean for next year.

Gypsy moth caterpillars are coming out of their pupal stage and now the moths are here. “You can see them writhing around there. They are getting ready to emerge into adults,” said Margaret Skinner, a researcher at the University of Vermont. She says it’s around this time of the year when the male moths fly away and the females lay eggs on trees, the last we will see of them until next year. “The good thing about gypsy moths are there is only one generation a year, so these eggs are not going to hatch until next April

Skinner says one reason for the outbreak this year that devastated trees around the region was that a fungus that helps control their population was not as prevalent due to the dry spring. “This is part of the natural cycle. We may not like it but it is part of the cycle, and the reason the cycle changed was because we had a different natural enemy, and that was this fungus.”

“I don’t think we can really control or prevent an outbreak such as this,” said Kathy Decker with the Vermont Department of Forests, Parks and Recreation. She says while staff will monitor the egg count this year, it doesn’t always mean a high level of caterpillars next year, making it hard to predict the damage. “You can’t. It’s not a predictable thing to say, ‘Oh, you reach a threshold of this egg mass, therefore you are going to have this level.’”

Skinner says that most trees should survive and are even coming back already. She says it’s important to not forget about the emerald ash borer, the Asian longhorned beetle, and other invasives that can be even more harmful to trees.

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Infestation: Gypsy moth caterpillars munch their way across our region

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