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Hemlock Wooly Adelgid - Identification and Control


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Introduction to the Hemlock Wooly Adelgid
An infested hemlock bough

An infested hemlock bough

Kim Nix/ About Forestry
The Eastern Hemlock is a favorite tree of mine. It is not a tree of commercial importance but rather one of the most beautiful trees in the forest, extremely beneficial to wildlife and improves our quality of water. You will be looking at a personal pictorial as these are photos of my trees and they are dying.

Eastern hemlock and Carolina hemlock are shade tolerant and long-lived tree species found in eastern North America. Both survive well in the shade of an overstory, although eastern hemlock has adapted to a variety of soil types. The species natural range extends from Nova Scotia to northeastern Minnesota, southward into northern Georgia and Alabama, and east up the Appalachian Mountains.

The eastern and Carolina hemlock is now under attack and in the early stages of being decimated by the hemlock wooly adelgid (HWA) or Adelges tsugae. Adelgids are small, soft bodied aphids that feed exclusively on coniferous plants using piercing-sucking mouth parts. They are an invasive insect and thought to be of Asian origin.

The cottony-covered insect hides in its own fluffy secretions and can only live on hemlock. The hemlock wooly adelgid was first found on ornamental eastern hemlock in 1954 in Richmond, Virginia, but was not considered a serious pest because it was easily controlled with pesticides. HWA became a pest of concern in the late 1980s as it spread into natural stands. It now threatens the entire hemlock population of the eastern United States.

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