Predators collected from balsam woolly adelgid and Cooley spruce gall adelgid in western Oregon and Washington, U.S.A., with reference to biological control of hemlock woolly adelgid (Hemiptera: Adelgidae)

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The hemlock woolly adelgid (Hemiptera: Adelgidae: Adelges tsugae Annand) is an invasive insect, introduced from Japan to eastern North America, where it causes decline and death of hemlock trees. There is a closely related lineage of A. tsugae native to western North America. To inform classical biological control of A. tsugae in the eastern USA, the density and phenology of three native western adelgid specialist predators, Leucopis argenticollis (Zetterstedt), Le. piniperda (Malloch) (Diptera: Chamaemyiidae), and Laricobius nigrinus Fender (Coleoptera: Derodontidae), were quantified in the Pacific Northwest. Infested branches were collected from western hemlock (Pinaceae: Tsuga heterophylla (Raf.) Sarg.) at four sites around the Puget Sound, Washington and three sites in Oregon. Immature Leucopis were identified to species using DNA barcodes. Leucopis argenticollis was roughly twice as abundant as Le. piniperda. Laricobius nigrinus larvae were more abundant than the two species of Leucopis during the egg stage of the first adelgid generation, but Leucopis were present as feeding larvae during the second adelgid generation when La. nigrinus was aestivating in the soil, resulting in Leucopis being more abundant than La. nigrinus across the entire sampling period. Adelges tsugae and La. nigrinus densities were not correlated, while A. tsugae and Leucopis spp. densities were positively correlated. Leucopis spp. and La. nigrinus densities were negatively correlated. These results support the complementary use of La. nigrinus and the two Leucopis species for biological control of A. tsugae in the eastern USA, and point to the need for further investigation of spatial and temporal niche partitioning among the three predator species.

Section: Discussionmentioning

confidence: 99%

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

Rose

Ross

Havill

et al. 2019

Self Cite

“…nigrinus than adult Leucopis spp. and overestimates the abundance of the former compared with the latter (Ross et al , 2011). Therefore, the numbers from the clipped branch sampling technique used in this study are probably more representative of the relative abundance of the two genera of predators.…”

Section: Discussionmentioning

confidence: 99%

“…argenticollis or Le. piniperda collected in association with A. tsugae , although both species have been collected in association with other Pineus and Adelges species in other parts of North America (Ross et al , 2011). The abundance of Leucopis spp.…”

Section: Introductionmentioning

confidence: 99%

Seasonal phenology and abundance ofLeucopis argenticollis, Leucopis piniperda(Diptera: Chamaemyiidae),Laricobius nigrinus(Coleoptera: Deridontidae) andAdelges tsugae(Hemiptera: Adelgidae) in the Pacific Northwest USA

Kohler

Wallin

Ross

2016

Adelges tsugae infested western hemlock trees were sampled periodically for 1 year at two locations in Oregon and Washington to compare the phenology and abundance of three associated predators (Leucopis argenticollis, Leucopis piniperda, and Laricobius nigrinus) and their host. On each sample date, two 3-10 cm long terminal twigs were collected from each tree and brought to the laboratory to count all life stages of A. tsugae and the three predators. Peak larval abundance of Leucopis spp. and La. nigrinus coincided with the presence of A. tsugae adults and eggs. Leucopis spp. larvae were present for a much longer period of time than were La. nigrinus larvae. Furthermore, Leucopis spp. larvae were present during both the progrediens and sistens egg stages, while La. nigrinus larvae were only present during the progrediens egg stage. Overall, we collected 2.3-3.5 times more Leucopis spp. of all life stages than La. nigrinus. These results support the continued study of Leucopis spp. from the Pacific Northwest as biological control agents for A. tsugae in the Eastern USA.

“…L. nigrinus, L. argenticollis , and L. piniperda were the only adelgid-specific predators that were both frequently encountered and abundant in the survey. This was the first record of either L. argenticollis or L. piniperda collected from A. tsugae , although both species have been collected in association with other Pineus and Adelges species in other parts of North America (Ross et al , 2011). A more recent study in Oregon and Washington found 2.3–3.5 times more Leucopis spp.…”

Section: Introductionmentioning

confidence: 92%

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

Motley

Havill

Arsenault-Benoit

et al. 2017

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.