Modeling the potential roles of biological controls in the management of the hemlock woolly using life history analyses in a climatic context

The invasive hemlock woolly adelgid (Adelges tsugae) poses a threat to the stability and structure of of eastern hemlock stands in North America.  Efforts to manage the adelgid have included the development of classical biological controls and several host-specific Laricobius and Chamaemyiid predators have been identified as candidate species.  To accelerate the assessment of potential impacts by these predators, a population model that integrates available information for the hemlock woolly adelgid including known density dependent population dynamcis for the adelgid, the role of winter temperatures on the adelgid, and limited information on the timing of feeding by predators has been developed.  Though the models continue to evolve as new data becomes available, they currently suggest that the relative impact of three biological controls currently being released may vary, based on the timing of their feeding.  The data also suggest the control of adelgid populations may benefit from the application of a suite of predator species with complimentary feeding behaviors.  Temperature on the landscape plays a role in determining the density of adelgids, though the effects of temperature and predation appear additive.  As new information becomes available, these models will continue to be expanded to help assess the role biological controls may play in the maintenance of hemlock as a forest resource in eastern North America.