Host range studies with Scymnus coniferarum, a potential biological control agent of HWA

Hemlock woolly adelgid (HWA), (Adelges tsugae Annand), is an invasive pest of eastern hemlock (Tsuga canadensis (L.) Carrière) in the eastern North America. Scymnus (Pullus) coniferarum Crotch (Coleoptera: Coccinellidae) is a small lady beetle that preys on HWA in the western U.S. and is absent from hemlock stands in the East. While preliminary studies have shown its release to be of limited risk, more information is needed on the life history of S. coniferarum to determine if it will be a suitable biological control agent for HWA in the eastern US. Host-range tests for Scymnus coniferarum were conducted in Virginia Tech’s quarantine facility in Blacksburg, VA. We looked at host specificity for S. coniferarum in a series of no-choice and paired choice feeding, oviposition and development studies. These host-range tests involved Adelges tsugae (HWA), Adelges piceae (BWA), Adelges laricis (Larch adelgid) and Paraprociphilus tessellates (Woolly alder aphid). Overall, S. coniferarum fed and laid more eggs on HWA than any other species. Importantly, S. coniferarum only completed development on HWA and BWA, another adelgid pest species in the target release area. The results of this host-range analysis indicate that S.coniferarum is a generalist predator that only completes development on the host family Adelgidae. These data support S. coniferarum as a potential biological control agent of HWA.