Phenology of Leucotaraxis argenticollis, a specialist predator of the invasive hemlock woolly adelgid, in the eastern US

Leucotaraxis argenticollis is one of two silver fly species recently released into the eastern US as part of a biological control program for the hemlock woolly adelgid (HWA), Adelges tsugae. For a biological control program to succeed, it is important to understand the agent’s phenology in its introduced range. In the Pacific Northwest, Leucotaraxis argenticollis may have two generations per year, and larvae are present when HWA adults and eggs are present. However, the phenology of Leucotaraxis argenticollis has not been evaluated in the eastern US. This study examined the phenology of this species in the eastern US at one site in New York and another in Virginia. At each site, 30 eastern hemlock branches with medium to high HWA densities were selected. Establishment of Leucotaraxis argenticollis in the eastern US has yet to be documented, therefore fine mesh cages were applied. Ten adult flies (5 females: 5 males) were released into each cage while HWA sistens were starting to produce eggs. Branch clippings were taken biweekly for evaluation. For each evaluation, the life stages of both Leucotaraxis argenticollis and HWA were recorded from February – October, and branches were collected to detect adult emergence from overwintering puparium. The synchrony of the life cycles between the predator and prey will be discussed in the context of ongoing biological control activities of this pest.