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Managing Invasive Species


Hemlock Woolly Adelgid

Hemlock Woolly AdelgidThe hemlock woolly adelgid (HWA) is an exotic insect pest of eastern and Carolina hemlocks. HWA now occurs from southern Maine to northeastern Georgia and as far west as eastern Tennessee. This area represents about one-half of the native range of hemlock in the eastern U.S. The entire range of eastern hemlock may become infested within the next few decades. In Virginia, New Jersey, Connecticut, and portions of Pennsylvania extensive tree mortality and decline are common. This insect adversely affects an important and unique habitat for many wildlife species. Loss of hemlocks along streams adversely affects water resources. There are no practical means available to manage HWA in forest situations. Biological control using predators of HWA may prove to be the most practical means of slowing the spread and minimizing the impacts caused by HWA. Predatory beetles from China are being released; these beetles have successfully overwintered, reproduced, and reduced HWA populations on individual trees, but their overall effectiveness remains unclear.

  • Hemlock is an ecologically critical tree in the east, especially in riparian areas and is also commonly used as an ornamental in urban/suburban areas.
  • Forest Service supports biological control efforts in 15 eastern states.
  • Predatory beetles are being reared and released in an effort to reduce damage and to slow the spread of this exotic pest.
  • In 2002 the Forest Service completed a comprehensive strategic plan for managing HWA and formed a multi-agency steering committee to monitor its implementation.
  • 2003 funding was increased to begin implementing the strategic plan.