Hemlock Woolly Adelgid (Hemiptera: Adelgidae) Management in Forest, Landscape, and Nursery Production

Hemlock woolly adelgid, Adelges tsugae (Annand) (Hemiptera: Adelgidae), has caused significant damage to both eastern [Tsuga canadensis (L.) Carriere] and Carolina hemlock (Tsuga caroliniana Englemann) (Pinales: Pinaceae) since it was first reported in the eastern United States. This adelgid is particularly damaging to these hemlock species due to a lack of co-evolved plant defenses and natural enemies able to suppress hemlock woolly adelgid populations. Management of hemlock woolly adelgid relies heavily on insecticides to prevent death of vulnerable trees. Biological control programs have released natural enemies of hemlock woolly adelgid to aid in control at the landscape level. Quarantine restrictions on hemlock are in place in some regions of the United States and Canada. These quarantines impact sales and shipment of hemlock trees from nurseries as well as other hemlock products. A review of insect biology, description of life stages, damage, management options, and quarantine restrictions for hemlock woolly adelgid is presented.