The flies lay their eggs on the leaves favored by winter moths, and the caterpillars consume the eggs along with the leaves. They hatch inside the pupating caterpillar, which is killed by the fly larvae feeding on it. No moth outbreak in the fall, and, come springtime, it is the fly that rises from the dirt.
Every year, Elkinton’s team imports the flies from Canada and keeps them cool in a lab on Cape Cod. This year, about 30,000 flies will be released in about 10 spots throughout Massachusetts, Rhode Island, and coastal Maine.
Elkinton said he gets one question a lot: Could the fly itself become a problem?
“The answer is no,” he said. “When the winter moth declines, the fly itself declines. It will basically eliminate its own food supply. The fly and the moth will basically exist at low densities, forever more.”
The winter moth project, however, relies entirely on federal grants to continue; money from the state has dried up, and it’s a battle every year to keep the project alive, said Elkinton.
Gooch had been giving Elkinton a portion of his federal funding, until his budget was cut, too. “If he doesn’t get funded, that work will slow down, and not be done. The flies that are out there will still be out there, but the winter moths will spread fast,” said Gooch.
The winter moth has devastated parts of Rhode Island, Elkinton said, and this year there is an outbreak in Harpswell Neck, Maine. “The winter moth, it has such a large head start. It’s already way ahead,” said Gooch. If Elkinton’s work doesn’t continue, he added, “you might not be able to stop it.”
Evan Allen can be reached at firstname.lastname@example.org.