The Hemlock Woolly Adelgid (Adelges tsugae Annand; HWA) is an exotic invasive species introduced to the eastern US from Japan. The introduction of a biological control from one of HWA’s native ecosystems presents a potentially cost-effective solution for pest management at the landscape scale. Several HWA predators are being evaluated in eastern North America, including two species of silver fly from the Pacific Northwest (PNW), Leucopis argenticollis and Leucopis piniperda (Leucopis spp.). In addition to being the most abundant predators found in association with HWA in the PNW, Leucopis spp. ability to survive and reproduce in field conditions on the east coast motivate further research for their use as biological controls. However, little is known about Leucopis spp.’s habitat niche in the PNW nor the mechanisms that allow the two species to seemingly occupy the same ecological niche. We evaluated the spatial and bioclimatic drivers of Leucopis spp. distribution using a combination of field sampling, genetic analysis, spatial analysis (GIS), and species distribution modeling (using the R package Biomod2). We are using our results to forecast suitable regions on the east coast for Leucopis spp. establishment and survival.
Results/Conclusions
Our studies’ initial results corroborated evidence that Leucopis spp. from the PNW can survive predating HWA on the east coast. Phenological discrepancies and environmental factors, however, impacted Leucopis spp. establishment, survival and fecundity during the study period. This is evidenced by Leucopis spp. and eastern HWA asynchronicity in the summer of 2018, which impacted the availability of Leucopis spp. at the time of HWA emergence. Additionally, environmental conditions (high precipitation in the southeastern US) may have impacted Leucopis spp. ability to establish in 2017, resulting in almost no survival in North Carolina sites. Ecological niche differences between Leucopis species may also have affected their success in the east as Motley. et al found in 2016 that all resulting specimens from a study site in New York were L. argenticollis while specimens from Tennessee were a mix of both species. The modeling approach used to assess the spatial and bioclimatic drivers of Leucopis spp. populations in the PNW will be presented. These results will aid in minimizing non-target impacts of their release and increasing the efficiency and success of collection and release of Leucopis spp. in the east.