Density-Dependent Feedback and Population Cycles in Adelges tsugae (Homoptera: Adelgidae) on Tsuga canadensis

Abstract

Studies in a hemlock plantation and in four hemlock forests in Connecticut revealed that hemlock woolly adelgid, Adelges tsugae Annand, severely reduced the growth and survival of Tsuga canadensis (L.) Carriere, which had a major impact on the subsequent performance and population dynamics of this insect. The presence of adelgids at all but relatively low densities (93% of the adelgids produced in each of the subsequent 3 yr became sexuparae; in the fourth year only sexuparae were produced. Density-dependent production of the unsuccessful sexuparae played a major role in the decline of A. tsugae populations on their deteriorating host.