The hemlock woolly adelgid (HWA) is a small insect that threatens the health and survival of eastern hemlock trees (mainly Tsuga canadensis).  Woolly adelgids were introduced from Asia in the 1950s and have spread to Kentucky.  HWA have killed large number of the hemlocks in infested areas and there appears to be little resistance to the insect in our native hemlocks. 

What is it?

HWA, Adelges tsugae, are very small insects that develop a distinctive shelter of white wool-like hairs as they mature, making them look like very small cotton balls attached to the undersides of hemlock needles.  These insects attach to the bark at the base of needles and, similar to aphids, suck sugars from the trees.
 

What does HWA do?

Insects feed on the starch in the sap of trees, robbing the tree of energy. Their feeding causes needles to dry up, turn a grayish color and fall then off.  In addition, because they kill the apical buds, HWA prevents the tree from producing new growth. Because infestations are so severe, HWA can kill a tree within 4 to 10 years.  In addition, infestation can weaken trees making them highly susceptible to other problems.

 Hemlock Woolly Adelgid Resources:

• US Forest Service, Hemlock Woolly Adelgid