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  • Parasitic flies to be released as biocontrol for winter moth

     Entomologists at the Maine Department of Agriculture, Conservation and Forestry's Maine Forest Service (MFS) are continuing their battle against winter moth. On Wednesday, September 12, they will be setting out parasitic flies (Cyzenis albicans) in Bath as part of a biocontrol project to control the invasive winter moth (Operophtera brumata). In several Massachusetts locations, the parasitoids have been successful in reducing winter moth populations to non-damaging levels.

    The flies are currently in cocoons for the winter and will be set out in a cage buried in the ground until spring. In early May when the flies start to emerge the cage will be opened to release them to go to work on the winter moth.

    Part of a larger release program

    The release was part of a larger release program, undertaken in conjunction with the University of Massachusetts, with funding from the U.S. Department of Agriculture to control the winter moth across New England. Flies have been released in six other locations in south coastal Maine starting in 2013 and are starting to become established in Kittery, Cape Elizabeth and Vinalhaven. In several locations in Massachusetts, where the flies have been released since 2005, the parasitoids have been successful in reducing winter moth populations to non-damaging levels.

    Winter moth (Operophtera brumata) & parasitic flies (Cyzenis albicans)

    Both the winter moth and their parasites are originally from Europe. Winter moth defoliation was first recorded in Maine in 2012 and now the moths have been detected from Kittery to Mount Desert Island. The larvae (caterpillars) of winter moth feed on the leaves deciduous trees and shrubs such as oaks, maples, apples and blueberries, in early spring. Heavy defoliation for several consecutive years leads to branch dieback and tree mortality. Winter moth defoliation has contributed to tens of thousands of acres of oak mortality in Massachusetts and now there is oak mortality in Cape Elizabeth.

    The parasitic flies only attack winter moth and the adult flies are around for just a few weeks in May making it a good biocontrol agent. They have been successfully used as a control strategy in Nova Scotia, parts of western Canada and the US, as well in southern New England.