Recruitment of native parasitic wasps to populations of the invasive winter moth in the Northeastern United States

Authors: BROADLEY, HANNAH - University Of Massachusetts; Kula, Robert; BOETTNER, GEORGE - University Of Massachusetts; ANDERSEN, JEREMY - University Of Massachusetts; GRIFFIN, BRIAN - University Of Massachusetts; ELKINTON, JOSEPH - University Of Massachusetts

Submitted to: Biological Invasions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/26/2019
Publication Date: 6/7/2019
Citation: Broadley, H.J., Kula, R.R., Boettner, G.H., Andersen, J.C., Griffin, B., Elkinton, J.S. 2019. Recruitment of native parasitic wasps to populations of the invasive winter moth in the Northeastern United States. Biological Invasions. 21:2871-2890.

Interpretive Summary: Parasitic wasps attack crop and forest pests that cause billions of dollars of damage annually. The parasitic wasps treated in this paper attack winter moth, an exotic invasive forest pest in North America that causes damage to blueberry, apple, and cranberry. This research uses DNA sequence data and morphology to determine the identities of these wasps. The effect of these native wasps on an invasive population of winter moth in the northeastern United States was also assessed. We found that recruitment of these wasps to the invasive winter moth population is likely playing a significant role in regulating population outbreaks and is likely aiding in classical biological control efforts. Wasps in the genus Pimpla inflicted 98% percent of the parasitism detected, resulting in an annual average of 15-40% mortality on pupae not depredated. Parasitism was greatest at the leading edge of the winter moth population spread and when winter moth pupal density was high. The Pimpla wasps were identified as one species based on morphology but were found to comprise two cryptic species based on DNA sequence data. This paper will be useful to scientists conducting research on winter moth, personnel responsible for controlling and regulating winter moth, and personnel generally involved in pest management.

Technical Abstract: Ecological communities may be resistant to invasive species through a combination of top-down and bottom-up mechanisms, including predation, competition, parasitism, and disease. In particular, natural enemies that cross over from native species to use newly introduced non-native species as hosts can influence invasive species population dynamics and may slow down invasions. However, research on parasitism in biological invasions is lagging behind research on biological invasions in general. We used the model species winter moth (Operophtera brumata) to study the effect of recruitment of native parasitoids on an invasive population of winter moth in the northeast United States. We deployed sentinel pupae over four years across this population’s range, identified recovered parasitoids, and measured the rate of parasitism by native sources across years, seasons, invasion history, and host densities. Native Pimpla wasps inflicted 98% percent of the parasitism detected, resulting in an annual average of 15-40% mortality on pupae not depredated. Pimpla were present across all years, seasons, and sites. Parasitism was greatest at the leading edge of the winter moth population spread and when winter moth pupal density was high (i.e. positive density-dependence). The wasps were morphologically identified as Pimpla aequalis; however, using a multilocus genetic comparison approach, they were determined to comprise two cryptic species. Overall, this study shows that recruitment of these native wasps to the invasive winter moth population is likely playing a significant role in regulating population outbreaks and is aiding in biological control of winter moth.