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Research

Exotic herbivores on a native tree

Project Leaders: Colin Orians, Coco Gómez, Evan Preisser and Carol Thornber

The invasive Hemlock Woolly Adelgid (Adelges tsugae), accidentally introduced from Japan in the 50’s, is causing widespread and rapid decline of Eastern Hemlock (Tsuga canadensis) in North America. Despite fears that the hemlock woolly adelgid would eliminate hemlocks from southern New England, mortality in this area is occurring much more slowly than predicted.

It has been hypothesized that the interaction with another exotic insect, the Elongate Hemlock Scale (Fiorinia externa), might be the cause for this reduced mortality. Possible mechanisms behind this interaction may include inter-specific competition for resources and/or induced responses. We are trying to understand the basis for this variation and focusing on the nutritional, defense-related, morphological and biomechanical changes that might explain differential mortality.

This collaborative project seeks to understand plant-mediated interactions between these two insects in order to identify physiological mechanisms underlying their individual and combined impact. At Tufts, we are studying nutritional, defense-related, morphological and biomechanical changes that ultimately might explain mortality or lack thereof in response to herbivore feeding.

Our experimental approaches range from green house studies to field experiments and landscape surveys. Understanding how the interaction of invasive species changes the eastern hemlocks physiology during the course of infestation is crucial in assessing the impact of these destructive pests and to establish appropriate management.