Photo: D. Elswit

Land Trust Partnering with Cornell University to Combat Threats to Hemlock Trees

The Land Trust is partnering with Cornell University to combat the hemlock woolly adelgid (HWA) as part of the New York State Hemlock Initiative (NYSHI). NYSHI integrates state-wide research, management, and outreach to conserve New York State’s hemlocks.

The HWA, an invasive pest from Japan that threatens to kill the eastern hemlock found in many of the forests and gorges in the region, reached the Finger Lakes in 2008. In response, the Land Trust and NYSHI created a partnership to establish biocontrol populations—both Laricobius beetles and Leucopis silver flies—on several nature preserves. This year, NYSHI released silver flies on hemlock trees at the Land Trust’s Ellis Hollow and Lindsay-Parsons Biodiversity preserves.

Photo: FLLT

The flies are released into fine mesh bags and placed on one localized hemlock branch where they will lay their eggs. When the fly eggs hatch, the larvae will eat HWA eggs, thus reducing the population of hatching HWA in the late spring and early summer.

“Ecologically speaking, hemlocks are a foundation species, providing the habitat upon which a number of species depend for survival,” said Cornell University forest entomologist Mark Whitmore. “They provide winter cover for mammals, shelter migrating birds, and their shade maintains cool water in streams necessary for breeding native brook trout. Hemlocks are an irreplaceable part of the eastern forests and so common we take them for granted. It’s hard to imagine that they might disappear, but we’ve learned hard lessons from the hemlocks’ destruction in the southern U.S., and are working hard to implement a long term solution.”

Landowners are especially important in efforts to slow and contain the spread of HWA. In New York, 76% of the forest is privately owned so it is crucial that forest owners know about the threat of HWA and report any findings. More on HWA, including identification guides and management information, can be found at