Hemlock Woolly Adelgid
Hemlock Woolly Adelgid. Photograph credit:
Chris Evans, The University of Georgia
The hemlock woolly adelgid (Adelges tsugae) (HWA) is native to parts of Asia and was first discovered in New York in 1985. It is in the family Adelgidae, which is related to aphids. The adelgid uses long mouth parts to extract sap and nutrients from hemlock foliage, this prevents free growth, causing needles to discolor from deep green to grayish green, and to drop prematurely. The loss of new shoots and needles seriously impairs tree health. Infestation is usually fatal to the host after several years. Valued plantings of the shade-loving eastern hemlock (Tsuga canadensis) can be ravaged by the hemlock woolly adelgid, and the natural stands of hemlock in the forests and parks in upstate New York would be greatly affected if the pest spreads to those locations. The wind, birds, other wildlife and the movement of infested host material (wood) by humans are all factors in the dispersion of the adelgid.
From the first discovery of the hemlock woolly adelgid in the Hudson Valley in the 1980's, the insect has spread north and west to the Catskills, the Capital Region and even the Finger Lakes and other parts of Western New York. Currently 25 New York counties are infested with the hemlock woolly adelgid.
- View a video about the hemlock woolly adelgid's destruction of hemlock forests (leaves DEC website, 23 minutes).
- Article on the effect of cold temperatures on invasive pest species (PDF, 1 MB) by Mark Whitmore of Cornell University.
- Fact Sheet on hemlock woolly adelgid (PDF, 290 KB)
To learn more about hemlock woolly adelgid, including management options, please see the Links Leaving DEC's Website in the right column. To report a sighting of this insect, go to "Look for and Report Hemlock Woolly Adelgid" below or in the column to the left.
More about Hemlock Woolly Adelgid:
- Look for and Report Hemlock Woolly Adelgid - How to Identify the Hemlock Woolly Adelgid
- Progression of Hemlock Woolly Adelgid in NYS - View the progression of Hemlock Woolly Adelgid across NYS by year from 1987 to 2013.
- Hemlock Woolly Adelgid Photograph - A Close-up Photo of Hemlock Woolly Adelgid
- Hemlock Woolly Adelgid Map - Map showing towns and dates when HWA was first identified.