Feeding byLeucopis argenticollisandLeucopis piniperda(Diptera: Chamaemyiidae) from the western USA onAdelges tsugae(Hemiptera: Adelgidae) in the eastern USA

Abstract

Leucopis argenticollis (Zetterstedt) and Leucopis piniperda (Malloch) are known to feed on the lineage of Adelges tsugae Annand that is native to western North America, but it is not known if they will survive on the lineage that was introduced from Japan to the eastern USA. In 2014, western Leucopis spp. larvae were brought to the laboratory and placed on A. tsugae collected in either Washington (North American A. tsugae lineage) or Connecticut (Japanese lineage). There were no significant differences in survival or developmental times between flies reared on the two different adelgid lineages. In 2015 and 2016, western Leucopis spp. adults were released at two different densities onto enclosed branches of A. tsugae infested eastern hemlock (Tsuga canadensis (L.) Carr.) in Tennessee and New York. Cages were recovered and their contents examined 4 weeks after release at each location. Leucopis spp. larvae and puparia of the F1 generation were recovered at both release locations and adults of the F1 generation were collected at the Tennessee location. The number of Leucopis spp. offspring collected increased with increasing adelgid density, but did not differ by the number of adult flies released. Flies recovered from cages and flies collected from the source colony were identified as L.argenticollis and L. piniperda using DNA barcoding. These results demonstrate that Leucopis spp. from the Pacific Northwest are capable of feeding and developing to the adult stage on A. tsugae in the eastern USA and they are able to tolerate environmental conditions during late spring and early summer at the southern and northern extent of the area invaded by A. tsugae in the eastern USA.

Hemlock Woolly Adelgid (Hemiptera: Adelgidae) Management in Forest, Landscape, and Nursery Production

“…Native hemlock species exhibited severe stress and mortality in forest ecosystems as hemlock woolly adelgids spread. Historically, the range of hemlock woolly adelgid expanded from its original sites of infestation at an estimated rate of 3.6 ± 0.2 km/y along the eastern/western axis of its range and 5.8 ± 0.28 km/y in the northern/southern direction (Morin 2002). By the mid-1990s, hemlock woolly adelgid’s range was expanding at a rate of 16–24 km/y (Souto et al.…”

“…(Fig. 3D) from populations in the northwest United States are currently promising biocontrol agents (Motely et al. 2017).…”

“…In a recent cage study, Leucopsis spp. persisted in eastern U.S. climate and fed on hemlock woolly adelgid adults (Motley et al. 2017).…”

Hemlock Woolly Adelgid Adelges tsugae (Annand 1928) (Insecta: Hemiptera: Adelgidae)

“…Since 2015, considerable work was done to release the west coast strain of Leucopis spp. into eastern North America (Motley and Havill 2017). While adult predatory Laricobius beetles and their larvae are present during winter and spring, respectively, adult silver flies and their larvae are present in late spring and throughout summer, when aestivating hemlock woolly adelgid nymphs are present.…”

Coexistence of three specialist predators of the hemlock woolly adelgid in the Pacific Northwest USA

“…Although many details of the life cycle of both Leucopis species are unknown, previous research suggests that there are at least two generations per year based on peaks in abundance of different life stages (Kohler et al ., 2008; Grubin et al ., 2011). Furthermore, F1 adults were collected in as little as 28 days after adult flies were released onto caged hemlock woolly adelgid infested branches in Tennessee and New York indicating that the flies complete a generation in less than 4 weeks (Motley et al ., 2017).…”