Hemlock woolly adelgid hosts include spruce, yeddo spruce, tiger-tail spruce, eastern hemlock, Carolina hemlock, Chinese hemlock, Japanese hemlock, western hemlock, mountain hemlock, and southern Japanese hemlock.
In its native range within Asia, hemlock woolly adelgid is not a very serious or destructive pest. Population levels are controlled by natural enemies and by host resistance. The hemlock woolly adelgid was first reported in western Canada (British Columbia), in the 1920's and in the United States (Virginia), in the 1950's. In the eastern U.S., all sizes and ages of eastern hemlock, and Carolina hemlock are susceptible to hemlock woolly adelgid infestations. In British Columbia, damage to western hemlock has been minor.
Hemlock woolly adelgid was detected on one tree on one property in LaPorte County in 2012. The tree was lightly infested and was destroyed. Surveys in 2012 around the property did not detect other infested trees. Hemlock woolly adelgid is not estalished in Indiana.