Dr. Evan Preisser '93
Friday, April 5, 2013 at 1:10pm
Thompson Biology, 112 59 Lab Campus Dr, Williamstown, MA 01267
Biology Department Colloquium
The hemlock woolly adelgid Adelges tsugae (‘HWA’) is an invasive herbivore that poses a major threat to eastern hemlock (Tsuga canadensis) in eastern North America. High-density HWA infestations can kill even mature trees in 4-10 years; as a result, substantial hemlock mortality has occurred from VA to MA. Despite fears that HWA would remove hemlocks from southern New England, however, stand-level mortality in this area is occurring much more slowly than predicted. Although overwintering mortality of HWA has played a role in reducing hemlock mortality, another potential (but non-exclusive) explanation involves the recent rapid range expansion of a second introduced insect, the elongate hemlock scale Fiorinia externa (‘EHS’). While EHS can reduce hemlock growth and may be capable of killing stressed trees, its impact on tree health is minimal compared to that of HWA. Neither HWA nor EHS possess natural enemies capable of substantially limiting their population growth in the invaded range, and both are now abundant in southern New England. My lab has explored the interactions between these two insects and their common hemlock host, and the herbivores’ individual and joint impact on hemlock physiology. Understanding the interaction between these two invasive pests, both directly and indirectly through their shared host plant, may provide information important to controlling both threats.
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