Hemlock Woolly Adelgid (HWA)
The adelgid causes hemlock decline and mortality within 4-10 years of infestation in its southern range. During the fall and winter months, developing adelgids feed on young twig tissue, including starch reserves critical to the tree’s survival.
Common Name: Hemlock woolly adelgid (HWA)
Scientific Name: Adelges tsugae
Native Range: Asia, Northwest USA
Background
Hemlock woolly adelgid (HWA) is tiny, less than 1/16 inches long, and is dark reddish-brown to purplish-black in color. Its name derives from a white “wool-like” covering called an ovisac on mature egg laying adults.
The white, woolly ovisacs can be easily identified on the undersides of hemlock branch tips from late fall to early summer.
Habitat
HWA develops and reproduces on all hemlock species but attacks only Eastern and Carolina hemlocks.
NYS Distribution Map
NOTE: If you receive a “sign in” message, click cancel to continue. Confirmed observations of Water chestnut submitted to the NYS Invasive Species Database. For more information, visit iMapInvasives
Identification
Look for white woolly growths attached to the twig on the underside of the tree branches. Affected trees can eventually turn pale green or gray. In spring, affected trees lack new shoots/growth.
Impact
The adelgid causes hemlock decline and mortality within 4-10 years of infestation in its southern range. During the fall and winter months, developing adelgids feed on young twig tissue, including starch reserves critical to the tree’s survival.
Prevention and Control
Moving bird feeders away from hemlocks, removing infested trees from woodlots, and state quarantines may help to slow the spread, while insecticides and biological controls can be used for local suppression.
Additional Information
- Invasive Species Best Management Practices
- VIDEO: The New York State Department of Environmental Conservation (DEC) and partners have been working to control and prevent the spread of Hemlock Woolly Adelgid (HWA) on Forest Preserve lands around Lake George, a multi-year effort.
- Hemlock and HWA Identification Fact Sheet from NY Hemlock Initiative
- HWA Management Factsheet from NY Hemlock Initiative
