Adelgids (Hempitera: Adelgidae) are minute insects that include some invasive species detrimental to North American forests. Adelgids feed on various species of conifers. Two of the most significant pest adelgids in North America are the hemlock woolly adelgid (Adelges tsugae) and the balsam woolly adelgid (A. piceae). These adelgids cause severe, often mortal damage to native North American host species (hemlock woolly adelgid on eastern hemlocks Tsuga caroliniana, and balsam woolly adelgid on true firs). Biological control is one potential tactic for managing these pests. We investigated native predators as potential biocontrol agents of adelgids. Predators were associated with populations of A. piceae infesting subalpine fir, A. cooleyi infesting spruces, A. abietis infesting Norway spruce, A. lariciatus infesting cones of western larch, and Pineus strobi infesting western white pine (Pinus monticola). Most of the predators were found on western white pine. Two coccinellid beetles (Coccidophilus atronitens and Scymnus coniferarum) previously presumed to be specialists on pine needle scale, were also found to prey upon P. strobi and other adelgids. A third coccinellid and presumed scale specialist, S. humboldti consumed A. cooleyi. The research was both observational and experimental, and involved opportunistically surveying for potential predators in the field, followed by presenting predators with adelgids in the laboratory (both in no-choice and then choice trials). The successful predation on adelgids by diverse predators and the elucidation of predation preferences increase the understanding of ecosystem dynamics and provide information on potential steps for biocontrol.
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