Hemlock Woolly Adelgid

Hemlock Woolly Adelgid (HWA), originally from Asia, was first discovered in New Hampshire in Portsmouth in 2000. This small, wingless insect uses its piercing mouth parts to feed on small hemlock twigs. HWA, left untreated, can kill a tree in 4 to 10 years. Today there are many communities throughout the southeast and lakes region of New Hampshire with small infestations. In an effort to slow the spread of this pest, the NH Division of Forests and Lands developed an action plan, which includes a quarantine on hemlock material from all infected NH counties.

Untreated outbreaks of HWA weaken the tree an leave it susceptible to damage from other pests, such as elongate hemlock scale and hemlock borer. Therefore, maintaining trees in a healthy condition lessens damage by other pests.

The Basics and What to Do NH Pest Alert and Forest Service Pest Alert Wallet Card Look-Alikes Controlling HWA in NH Options for Managing Hemlock Forests Eastern Hemlock Forests Guidelines (1173 KB) HWA and Other Exotic Insects Susceptibility of Landscape Trees to Invasive Insects Brochure Poster Help Protect Our Trees -- Exotic Species Fact Sheet Important HWA Websites NH Division of Forests and Lands Maine Forest Service USDA Forest Service, Northeastern Area

Towns with infestations Treatment status (includes elongate hemlock scale) Harvard Forest's ecologist, David Orwig, discusses threats to our native forests.

Cooperating agencies:

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