Therefore, they leave the hemlock tree in search of spruce, the alternate host. However, since no suitable spruce host is available in North America, they soon die. Other adults produced at this time are wingless and are able to reproduce on hemlock. In the middle of June these wingless adults lay 50 to 300 eggs each in a cottony mass on the twigs. Crawlers hatch in early July and settle on the new growth but enter a non-feeding dormancy until October, when feeding resumes.
Nymphs feed and develop during the winter and mature by spring.
The eggs and nymphs, which are not attached to the plant via mouthparts are abundant from March through June and can be readily dispersed by wind, birds, deer and other mammals. Humans can also disperse the insect through various activities including moving infested plants. Adelgid feeding and its consequences. The HWA injures susceptible hemlocks by sucking sap and probably also by injecting a toxic saliva while feeding. This causes the needles on infested branches to desiccate, turn a grayish-green color, and then drop from the tree usually within a few months.