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Abstract
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.
Citation
Rose, Alexander; Ross, Darrell W.; Havill, Nathan P.; Motley, Kyle; Wallin, Kimberly F. 2020. Coexistence of three specialist predators of the hemlock woolly adelgid in the Pacific Northwest USA. Bulletin of Entomological Research. 110(3): 303-308. https://doi.org/10.1017/S0007485319000622.
