Variation in winter survival of the invasive hemlock woolly adelgid (Hemiptera: Adelgidae) across the eastern United States.

The hemlock woolly adelgid (Adelges tsugae Annand) is a small, aphid-like insect native to East Asia and western North America. First documented in the eastern United States in Richmond, VA, in 1951, it has spread to at least 17 states, where it causes increased mortality among both eastern and Carolina hemlocks (Tsuga canadensis Carrière and T. caroliniana Engelmann.

Temporal and spatial variation of terpenoids in eastern hemlock (Tsuga canadensis) in relation to feeding by Adelges tsugae.

The terpenoid content of eastern hemlock (Tsuga canadensis) foliage was measured over an annual cycle of development from bud opening, shoot elongation, shoot maturation, to bud-break at the start of the next growing season. The objective was to determine if variation in terpenoid composition is linked with spatial and temporal feeding preferences of the hemlock woolly adelgid (HWA; Adelges tsugae). The HWA has two periods of feeding over the course of 1 yr spanning two complete generations.