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Hemlock Woolly Adelgid

Hemlock Woolly AdelgidHemlock Woolly Adelgid (HWA), Adelgis tsugae, a destructive aphid-like insect pest of eastern and Carolina hemlock, is originally from Asia.

HWA feeds on trees of all ages. The insects attach themselves to the base of the hemlock needles and feed from the new twig growth with piercing-sucking mouthparts. The most noticeable aspect of infested hemlocks is the white masses at the base of needles on the twigs. The adults are small (1/32 inch), oval and reddish purple, although covered with white, waxy tufts.

Limb dieback may occur within two years of the initial infestation on seedlings and saplings. Heavily infested larger trees usually die within four years, although it may take longer than 10 years depending on proximity to other infested trees, tree size, the level of environmental stress and the quality of the growing site.

HWA is established in East Tennessee. In Tennessee our goal is to keep the infestation contained and prevent it from further spreading with the movement of nursery stock. In November 2013, HWA was found in Grundy County. There are now 37 counties in Tennessee that have infestations. The six US states with HWA quarantines are Maine, Michigan, New Hampshire, Ohio, Vermont and Wisconsin. Canada also has a HWA quarantine in effect.

The entry requirements for Hemlocks from infested or adjacent areas vary from state to state. A State Phytosanitary Certificate is required. The state summaries may be found at http://na.fs.fed.us/fhp/hwa/quarantines/quarantines.shtm or at the National Plant Board (NPB) laws and summaries site http://nationalplantboard.org/laws/. For example, Michigan's quarantine does not allow movement of hemlock from an infested or adjacent county into the state. For more information, contact the State Plant Regulatory Official in the state you're intending to move hemlock (contact information at NPB site) or contact the Tennessee Department of Agriculture (Gray Haun or Steve Powell) at 615-837-5137.

View Infested Area Map [PDF]

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