Evaluating the establishment success of Microctonus aethiopoides (Hymenoptera: Braconidae), a parasitoid of the alfalfa weevil (Coleoptera:Curculionidae), across the northern Great Plains of North America

Authors: Rand, Tatyana; PELLISSIER, MAKENZIE - University Of Wyoming; JABBOUR, RANDA - University Of Wyoming; LUNDGREN, JONATHAN - Ecdysis Foundation; Waters, Debra

Submitted to: The Canadian Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/13/2017
Publication Date: 2/2/2018
Citation: Rand, T.A., Pellissier, M., Jabbour, R., Lundgren, J.G., Waters, D.K. 2018. Evaluating the establishment success of Microctonus aethiopoides (Hymenoptera: Braconidae), a parasitoid of the alfalfa weevil (Coleoptera:Curculionidae), across the northern Great Plains of North America. The Canadian Entomologist. 150(2):274-277. https://doi.org/10.4039/tce.2017.65.
DOI: https://doi.org/10.4039/tce.2017.65

Interpretive Summary: Title: Evaluating the long-term establishment success of an alfalfa weevil biological control agent in the Northern Great Plains Problem: Alfalfa weevil continues to be the dominant economic pest of alfalfa throughout much of the United States. Biological control introductions have successful contributed to control of this pest in many regions, but the long-term establishment and efficacy of some key agents in the Northern Great Plains remains unknown. Accomplishment: ARS scientists, at Sidney, MT, resurveyed counties in which M. aethiopoides, an important parasitoid wasp attacking adult weevils, had been initially recovered following redistribution across Montana, Wyoming and South Dakota in the 1980’s. The goal was to gauge whether this species has become permanently established and, if so, assess levels of parasitism in the field. Outcome/Impact: Despite rearing more than 1000 weevils, no parasitoids were recovered from any of the locations sampled in our study, suggesting a widespread failure of M. aethiopoides to persist in the region. Thus, despite evidence that it is highly successful in other areas, M. aethiopoides, does not currently appear to be an important biological control agent of alfalfa weevil in the northern Great Plains. Re-introducing this agent from sources in nearby states may be an option for increasing the efficacy of biocontrol of alfalfa weevil in the Northern Plains.

Technical Abstract: The alfalfa weevil, Hypera postica (Gyllenhal) (Coleoptera:Curculionidae), is a destructive pest of alfalfa worldwide. The biological control parasitoid, Microctonous aethiopoides Loan (Hymenoptera: Braconidae), which attacks the adult stage weevils, was successfully introduced to the United States, and considered highly effective in the eastern and mid-western states. Redistribution efforts carried out throughout the 1980’s reported initial establishment across a number of states in the northern Great Plains, however follow up studies to assess long-term persistence and efficacy are lacking. Our objective was to resurvey the counties in which M. aethiopoides had been initially recovered following redistribution in Montana (Flathead and Petroleum counties), Wyoming (Platte county) and South Dakota (Brookings county), to gauge whether this species has become permanently established and, if so, assess levels of parasitism in the field. We collected adult weevils in early spring, from five fields in each county, and reared them in the laboratory to assess parasitism. Despite rearing more than 1000 weevils, no parasitoids were recovered from any of the locations sampled in our study, suggesting a widespread failure of M. aethiopoides to persist in the region. Thus, M. aethiopoides does not currently appear to be an important biological control agent of alfalfa weevil in the northern Great Plains. However, more intensive surveys will be required to assess the extent of the current distributional limits of this species throughout the region.