What is Hemlock Woolly Adelgid?

An invasive pest plaguing hemlocks in the Eastern U.S., the hemlock woolly adelgid (Adelges tsugae) is a tiny, exotic invasive species that gets its name from its woolly white appearance and because its host is the hemlock tree. It was first introduced to the United States in the 1920s.

Reddish-brown nymphs (or crawlers) hatch from the eggs and use their thread-like mouthpart to pierce a hemlock branch and suck sap from the branch, causing the hemlock needles to dry out and drop. This defoliation can cause the hemlock tree to die in as little as 3-6 years.

Hemlock woolly adelgid (HWA) has killed 90% of hemlock trees in Shenandoah National Park, VA, as well as vast stands of hemlocks in North Carolina, Eastern Tennessee and Northern Georgia.

In Northern Georgia, Valent Professional Products is working with a local applicator, AdelRid, to treat municipally-owned hemlocks for HWA. As with EAB in the Midwest, Valent Professional Products is supplying free Safari® Insecticide while the Legacy Tree Project works to inform local media and stakeholders about the threat still being posed by HWA in the area.

Identifying Hemlock Trees

What does HWA look like?

  • Hemlock woolly adelgid infestation

    Hemlock woolly adelgid infestation
    John A. Weidhass,
    Virginia Polytechnic Institute and State University, Bugwood.org

  • Hemlock woolly adelgid adult

    Hemlock woolly adelgid adult
    Michael Montgomery,
    USDA Forest Service, Bugwood.org

  • Hemlock woolly adelgid damage

    Hemlock woolly adelgid damage
    William M. Ciesla,
    Forest Health Management International, Bugwood.org

Find out more about HWA:

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