Hemlock woolly adelgid (HWA) is native to Japan and possibly China.
It was first observed in western North America in the early 1920's and
had moved east to Virginia by the 1950's. In the eastern United
States, HWA is now found from northern Georgia, north along the
Appalachian Mountains to southern New England. Movement of
live infested hemlocks, wind, birds, and mammals disperse it on a
local scale. Hosts include forest and ornamental hemlock trees (Tsuga
spp.). HWA is a serious pest of eastern hemlock and Carolina hemlock.
Size varies from 1/16 to 1/8 of an inch in length with piercing/
sucking mouthparts. All adults are female with each female producing
50-300 eggs in a lifetime. It produces increasing amounts of white,
woolly wax used to protect itself and its eggs. A sign of infestation is
the presence of what appears to be the tips of cotton swabs on the
bases of needles. Needle loss and twig desiccation, caused by the
insects feeding, hinders shoot growth. Needle loss is followed by
twig die-back, defoliation, and death, usually within four to six years
of infestation. Severe infestations can eliminate the hemlock
component from forest stands. |
