Hemlock Woolly Adelgid – An Update

Landowners, loggers and outdoor enthusiasts in southern Vermont are asked to be on the look out for the Hemlock Woolly Adelgid. This small insect feeds on new shoots causing discoloration, desiccation and needle loss. Tree mortality may occur in four to six years, although some trees have survived with sparse foliage for more than ten years. Infested areas have experienced extensive decline and mortality of both forest stands and urban/suburban landscape hemlocks.

Introduced from Asia, where it does little harm, this tiny insect was first spotted in the 1920s in western North America where the native hemlocks are resistant and there have been no major problems. Hemlock Woolly Adelgid was observed in Virginia in the early 1950s and has now spread to sixteen states from Georgia to Maine. Hemlock Woolly Adelgid has few natural enemies in the East and native eastern and Carolina Hemlocks are not resistant. In some southern areas, like the Shenandoah National Park, hemlocks are in danger of disappearing. Hemlock is an important component of the forest ecosystem and its loss would have wide ranging impacts on wildlife habitat, water quality, soil characteristics and aesthetics, to mention a few.

In recent years, there have been isolated introductions of infected nursery stock in Vermont that were quickly discovered and eradicated. In 2007, Hemlock Woolly Adelgid was found on mature, native trees in Vermont for the first time, prompting officials to ask the public to help watch for the intruder.

The most obvious sign of Hemlock Woolly Adelgid is the white, woolly mass found on the underside of twigs at the base of needles.

Suspected infestations should not be moved, but reported to the Department of Forests, Parks and Recreation.

Citizens can help slow the spread of Hemlock Woolly Adelgid by accepting only uninfested planting stock. Hemlock trees may not be brought into Vermont from infested counties. Before purchasing trees, ask where they came from and whether or not they are permitted.

Many new HWA infestations are located near bird feeders and bird baths. The adelgids are most likely to hitch hike on birds between March and July. Taking feeders and baths down for this period when spring food sources are becoming available will have minimal impact on birds but, may be effective in slowing the movement of Hemlock Woolly Adelgid.

For more information or to report a suspected sighting, contact your county forester or the Department of Forests, Parks and Recreation at 802-885-8822.