Phenology of Leucotaraxis argenticollis, a specialist predator of the invasive hemlock woolly adelgid, in the eastern United States.

In hemlock stands within eastern US forests, classical biological control has been one of the main strategies used to manage the hemlock woolly adelgid, Adelges tsugae Annand. Specialist predator species may offer a management solution to help regulate A. tsugae populations. In the Pacific Northwest, a suite of specialist predators has been a focus of research and includes 2 species of silver fly, Leucotaraxis argenticollis (Zetterstedt) and Leucotaraxis piniperda (Malloch) (Diptera: Chamaemyiidae). Leucotaraxis spp. phenology has been documented in the Pacific Northwest, but the phenology of either western Leucotaraxis species is unknown in the eastern United States. This study sought to document the phenology of Le. argenticollis in NY in 2021 and in VA in 2021 and 2022. Nylon mesh cages were applied over eastern hemlock branches infested with A. tsugae to contain Le. argenticollis adults. Biweekly and monthly branch samples were taken in 2021 and 2022, documenting all life stages of A. tsugae and of Le. argenticollis that were observed. In 2021 and 2022, Le. argenticollis adults and eggs were present during the oviposition stage of the 2 generations of A. tsugae. In addition, Le. argenticollis larvae were present when A. tsugae ovisacs had eggs and while A. tsugae nymphs of both generations were present. These observations indicate that Le. argenticollis phenology is well synchronized with A. tsugae in the eastern United States.