D3428: Assessing whole-tree cages to establish Leucotaraxis spp. in the Southern Appalachians

Silver flies (Leucotaraxis argenticollis and Le. piniperda) are currently being evaluated as spring predators of hemlock woolly adelgid (Adelges tsuage, HWA). These predatory fly species are native to western North America and have been identified as part of the predator complex that feeds on HWA on western species of Tsuga. While commonly collected in the western U.S., little is known of their ability to overwinter and establish in the eastern U.S. in areas of release, as very few silver flies have been recovered at release sites. One suspected reason for lack of recovery is that flies may disperse quickly following releases and experience Allee effects. Silver flies have been released in sleeve cages on branches of hemlock infested with HWA. However, few recoveries have been documented from sleeve cage studies. This study assesses utilizing whole-tree cages to determine the ability of silver flies to establish on hemlock species infested with HWA in the southern Appalachians, and to examine fly interactions with an existing beetle predator (Laricobius osakensis). Whole-tree cages were deployed on eastern hemlock trees at a hemlock orchard in Bent Creek Experimental Forest. The following predator treatments were replicated three times: uncaged control, caged control, only Le. argenticollis released in the cage, Le. argenticollis and La. osakensis released in the cage, only La. osakensis released in the cage. Predator establishment and abundance is monitored using periodic branch collections and eDNA sampling. Select findings of this ongoing project will be presented and discussed.