Abstract
The hemlock woolly adelgid (
Adelges tsugae (Annand)) is a serious invasive pest of hemlock trees in eastern North America. Multiple biological control agents have been the focus of research aimed at pest management and conserving hemlock communities. Three promising A. tsugae specialist predators are the beetle
Laricobius nigrinus (Fender) (Coleoptera: Derodontidae) and flies in the genus
Leucotaraxis (Diptera: Chamaemyiidae),
Leucotaraxis argenticollis (Zetterstedt), and
Leucotaraxis piniperda (Malloch). However, these flies are vulnerable to parasitism by wasps in the genera
Pachyneuron (Walker) (Hymenoptera: Pteromalidae) and
Melanips (Walker) (Hymenoptera: Figitidae). This study explores parasitoid wasp interactions with these
Leucotaraxis species in their native western North American range and potential impacts on the biological control program in the East.
Leucotaraxis, La. nigrinus, and parasitoid emergences were observed from adelgid-infested foliage collected from Washington State and British Columbia in 2018, 2019, and 2020. Undescribed species of
Pachyneuron and
Melanips emerged from puparia as solitary parasitoids. Parasitoid emergence was positively correlated with Leucotaraxis emergence. Percent parasitism increased between February and July, with the months of June and July experiencing higher parasitoid emergence than
Leucotaraxis. Differences in emergence patterns suggest that
Pachyneuron may be more closely associated with
Le. argenticollis as a host, and that
Melanips may be associated with
Le. piniperda. High parasitism in
Leucotaraxis had no effect on
La. nigrinus larval abundance, whereas the combined emergence of parasitoids and
Leucotaraxis was positively correlated with
La. nigrinus. This suggests that there is limited competition among these predators.
Keywords
Adelgidae,
biological control,
parasitoid,
host–parasitoid interactions
Citation
Celis, Sabrina L; Dietschler, Nicholas J; Bittner, Tonya D; Havill, Nathan P; Gates, Michael W; Buffington, Matthew L; Whitmore, Mark C. 2022. Hymenopteran Parasitoids of
Leucotaraxis argenticollis (Diptera: Chamaemyiidae) and
Leucotaraxis piniperda : Implications for Biological Control of Hemlock Woolly Adelgid (Hemiptera: Adelgidae) . Environmental Entomology. 51(5): 901-909. https://doi.org/10.1093/ee/nvac060.