Predatory performance evaluations of wild- and laboratory colonized-populations of Sasajiscymnus tsugae, an introduced predator of hemlock woolly adelgid

Hemlock woolly adelgid (HWA), Adelges tsugae Annand (Hemiptera: Adelgidae), an invasive pest from Japan, affects the health of hemlock trees (Tsuga spp.) in the eastern US. Biological control has been the strategy employed for long-term management of HWA. Since 1995, Sasajiscymnus tsugae (St) Sasaji and McClure (Coleoptera: Coccinellidae) have been mass reared and released in many states. However, limited recovery and uncertain efficacy raise concerns about the impact of this predator on HWA. Nearly all St released have been the progeny of the original founding colony (less than 100 beetles collected from Japan in 1994). This research aims to understand predatory performance that may differ between progeny of the original laboratory-reared St and a new colony founded with wild individuals collected in Japan in 2010. Predation of HWA by each colony was compared in the laboratory (in Petri dishes) and in the field (in sleeve cages). Combinations of males only, females only, and males and females from each colony were placed on caged branches in the field and removed after three weeks; survival and reproduction of St and consumption of HWA were assessed. A concurrent experiment using HWA-infested hemlock twigs in Petri dishes with the same predator combinations was conducted for 48 hours; survival of St and consumption of HWA were assessed. Preliminary laboratory results indicate that survival and feeding are not different between the two colonies. Results will be presented and discussed, and implications for further studies to assess differences between wild and domestic St colonies will be examined.