Winter Moth Declines: No longer a pest!

UMass-Amherst scientists claim victory over invasive Winter Moth, Operophtera brumata.

Cyzenis Albicans has been found to reduce winter moth populations

New England’s native forests and sensitive ecosystems are now free from the threat thanks to the work of a team of research scientists at UMass Amherst.  A year ago, UMass entomologist Joseph Elkinton reported, “After fourteen years, we have successfully converted Winter Moth, a major defoliator invading eastern New England, into a non-pest, presumably on a permanent basis.” Backyard trees like oak, maple, birch, fruit orchards, and blueberry crops and millions of dollars in pesticide costs have been saved.

“The object [was] to reduce the density of the invasive species to non-pest status,” Elkinton said. Using an approach called biological control, the scientists introduced a parasitic fly, known as Cyzenis Albicans, that only attacks Winter Moths. “Cyzenis Albicans does not prey on anything but Winter Moth. Other native inchworms are not attacked.”

Winter Moths arrived in Nova Scotia from Europe before 1950, with another invasion in New England in the 1990s. Defoliation occurred both north and south of Boston spreading over much of Eastern Massachusetts, Rhode Island, southeastern Connecticut, and coastal Maine over the next decade.

Researchers in Nova Scotia and British Columbia had found that Cyzenis Albicans reduced Winter Moth populations, so Elkinton and fellow UMass entomologist George Boettner began collecting and breeding specimens. They released 80,000 flies during the spring at about two dozen sites around New England. By July 2018, the Cyzenis Albicans fly populations were established at thirty-eight sites — and the Winter Moth population declined without the use of pesticides.

Male Winter Moths fly in December, giving them their name. They mate with wingless females who lay eggs on bark or in crevices on the stems of trees. Eggs hatch in spring and the green inchworms feed on buds and leaves of their host trees.

With funding by the Commonwealth of Massachusetts, the U.S. Forest Service, and the USDA’s Animal and Plant Health Inspection Service (APHIS), research was led by Joseph Elkinton, professor of entomology in the UMass Amherst Department of Environmental Conservation. The team included George Boettner, UMass entomologist, and Hannah Broadley, UMass postdoctoral researcher, along with Richard Reardon and Ronald D. Weeks Jr. of the USDA.

Winter Moth pamphlet and report are available from


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