A hemlock woolly adelgid infestation can destroy a hemlock tree in just a few years. The insect gets its name from the fuzzy, white masses that the females produce. Photo: Michael Montgomery, USDA Forest Service.
In New York, climate change may make it easier for an invasive species to continue its spread to hemlock forests further to the north.
The threat comes from the hemlock woolly adelgid, an aphid-like insect that feeds on hemlock trees. The species gets its name from the fuzzy, white masses that the females produce. The adelgid uses its long mouth to extract nutrients from hemlock needles. This disrupts the flow of nutrients in the tree. Needles dry out, turn color, and drop off. Larger limbs start dying off within a couple of years. Trees become badly damaged and in many cases die after several years.
Hemlock forests provide unique habitat for wildlife. Their shade helps keep soil and water temperatures cool and provide microclimates in which many plants and animals thrive.
The hemlock woolly adelgid was first discovered in the United States in Virginia in the 1950s. It is native to Asia and was likely introduced to the U.S. by accident. It has thrived along the east coast and has damaged hemlock forests from Maine to Georgia.
In New York State, the hemlock woolly adelgid was discovered in the 1980s. Infestations are now found in 25 counties. The infestations are clustered in two regions: the Hudson Valley, which includes most of the lower portion of the state, and the Finger Lakes. There is great concern over the possibility of the insects eventually spreading to the forests of upstate New York, including Adirondack Park.