Recovery of hemlock in Vermont from defoliation by the spring hemlock looper, Lambdina athasaria (Walker)

Abstract

Following an outbreak of spring hemlock looper in 1991, ten hemlocks in each of fifteen study plots were monitored annually through 1999. Although some mortality occurred within two years after defoliation, and additional mortality occurred in plots which were subsequently disturbed by logging, most defoliated trees recovered. Twenty-four percent of the trees with 90% defoliation and 43% with 100% defoliation were dead by 1999. Trunk and root collar wounds were more common on dead or unhealthy trees. Overall, tree crown condition improved. In the spring of 1993, only 14% of trees in heavily defoliated plots were in good condition. Six years later, 73% were rated as good. Trees with dead tops usually recovered, maintaining wildlife cover and other values, but the defect may affect timber quality. Three categories of risk are suggested by this study: 40% defoliation (mortality not expected), 50-80% (light risk in of mortality), and 90-100% (moderate risk of mortality). Stand assessment two years after defoliation by spring hemlock looper provides an accurate picture of expected mortality, as long as no additional disturbance occurs.

Parent Publication

• Proceedings: symposium on sustainable management of hemlock ecosystems in eastern North America

Citation

Burns, Barbara S.; Trial, Henry, Jr. 2000. Recovery of hemlock in Vermont from defoliation by the spring hemlock looper, Lambdina athasaria (Walker). In: McManus, Katherine A.; Shields, Kathleen S.; Souto, Dennis R., eds. Proceedings: Symposium on sustainable management of hemlock ecosystems in eastern North America. Gen. Tech. Rep. NE-267. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northeastern Forest Experiment Station. 177-180.