Hemlock Woolly Adelgid

The hemlock woolly adelgid (ah-del-jid) (HWA, Adelges tsugae) is an aphid-like, invasive insect that poses a serious threat to forest and ornamental hemlock trees (Tsuga spp.) in eastern North America. HWA are most easily recognized by the white “woolly” masses of wax, about half the size of a cotton swab, produced by females in late winter. These fuzzy white masses are readily visible at the base of hemlock needles attached to twigs and persist throughout the year, even long after the adults are dead.

HWA has been in New York for at least the past 20 years. Originally confined to the lower Hudson Valley, it has since moved north to near Albany and west of Buffalo. It was detected in the Finger Lakes region in 2008; subsequent investigation revealed that it was largely confined to the southern parts of Seneca and Cayuga Lakes. In the intervening years HWA has spread, and is now found at higher elevations south of Cayuga Lake and nearly to the north ends of Seneca and Cayuga Lakes; it’s also found in the Rochester area. Learn how to identify HWA infestations here.