Beetles, Silver Flies Being Used Against Hemlock Woolly Adelgid Infestations

Hemlock trees are being threatened by an invasive insect called the hemlock woolly adelgid (HWA). Only the size of a sesame seed, this tiny aphid-like insect has the ability to take down an entire forest by feeding on and weakening hemlock trees – causing mortality within 5-7 years if left untreated.

As a foundation species, hemlocks are an important component of forests and provide many beneficial ecological services, like filtering water, shading streams, and providing food and habitat for wildlife.

First detected in New York State in the 1980s, hemlock woolly adelgid is established in the Capital Region, the Catskill Mountains, the Finger Lakes Region, and Western NY. In 2017, HWA was discovered in Adirondack Park at Prospect Mountain in Lake George, and in 2021, it was discovered in Oswego County.

Hope for the hemlocks may come in the form of a predatory beetle, Laricobius nigrinus, and two silver fly species, Leucotaraxis argenticollis, and Leucotaraxis piniperda, which are biocontrol agents or natural predators of HWA from their native range. Through a collaboration with the New York State Hemlock Initiative, NYS Department of Environmental Conservation, NYS Office of Parks Recreation and Historical Preservation, Oswego County, USDA Forest Service, and SLELO PRISM the first HWA biocontrol release to take place in the Eastern Lake Ontario region will occur.

A total of 2000 L. nigrinus beetles will be released this October at the Mexico Point State Park, a 122-acre park on the eastern shore of Lake Ontario in Oswego County. These predators feed on HWA eggs, and adults, and over time they have the ability to suppress hemlock woolly adelgid and enhance the resiliency of our hemlock trees. When predators establish this release has promise to serve as a dispersal point for the Eastern Lake Ontario region, spreading to other important ecosystems in the area to combat HWA regionally.

To learn more about the research being done with the biocontrol agents for hemlock woolly adelgid visit the New York State Hemlock Initiative website.

Photo of Hemlock Woolly Adelgid provided by DEC.