UMass Scientists Battle Winter Moth Infestation with Release of Parastic Flies on North Shore

AMHERST, Mass. – A team of scientists led by Joseph Elkinton of the University of Massachusetts Amherst will release a few hundred parasitic flies at the iron rail property in Wenham on Monday, May 15 at 1:30 p.m. The release is part of an effort to control the winter moth, an invasive species that is stripping the foliage from many kinds of deciduous trees in towns from the North Shore to Cape Cod. The team released the parasitic flies in Hingham last year as part of a long term campaign to control the winter moth caterpillars. Both the insects come originally from Europe.

The fly, known as Cyzenis albicans, is an important natural enemy of the winter moth that has successfully controlled the moth in earlier invasions of Nova Scotia and the Pacific Northwest. The fly lays its own eggs on foliage that is eaten by winter moth caterpillars. The caterpillars consume the eggs, which hatch inside the caterpillar and develop into a larval fly. The winter moth caterpillars drop to the ground in late May to form pupae in the soil. Winter moth pupae containing the larval fly eventually die and an adult fly emerges from the pupae the following spring to attack more winter moth caterpillars.

Elkinton and his colleagues are confident that the fly will eventually suppress winter moth populations to harmless levels, although it will take a few years for a few hundred flies to catch up with a population of winter moths that numbers in the trillions. The fly was introduced in Nova Scotia in the 1950s and within six years the winter moth numbers dropped considerably and have remained low. The research team is also confident that the fly will not cause other problems. Research has shown that it attacks only the winter moth and will not attack other species of caterpillars.

The Cyzenis release project represents a cooperative effort between UMass, the USDA Forest Service, USDA Animal and Plant Health Inspection Service, the Massachusetts Department of Conservation and Recreation and Plymouth County Extension.

The flies being released were collected by scientists with the Canadian Forestry Service in Victoria, British Columbia. They were shipped to the USDA, APHIS quarantine facility at Otis Air Base on Cape Cod where they were reared by George Boettner, a technician in Elkinton’s lab. Eggs produced by these flies will be used to infect a large number of winter moth caterpillars in the laboratory so that many more flies will be available next year for release in Massachusetts.