Exotic herbivores on a native tree
Project Leaders: Colin Orians, 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.