20 August 2021 Mason Bees (Hymenoptera: Megachilidae) Exhibit No Avoidance of Imidacloprid-Treated Soils
Christine Cairns Fortuin, Kamal J. K. Gandhi
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1) Many wild bee species interact with soil either as a nesting substrate or material. These soil interactions create a risk of exposure to agrochemicals such as imidacloprid or other neonicotinoid pesticides that can persist in soil for months after application. At the landscape level, concentrations of imidacloprid residue in soil are limited to the immediate treatment area, and thus risks to soil-interacting bees could be low if they avoid contaminated soils. 2) We utilized Osmia lignaria (Say), a solitary cavity nesting bee which collects mud to partition and seal nests, and conducted two laboratory experiments to test whether nesting females select or avoid soils containing various levels of imidacloprid residue. For the first experiment, we assessed behavioral responses of females to treated soil utilizing a choice arena and pairing various choices of soil with imidacloprid residues ranging between 0 and 780 ppb. For the second experiment, we developed a laboratory assay to assess soil selection of actively nesting O. lignaria, by providing choices of contaminated soil between 0 and 100 ppb and 0 and 1,000 ppb to nesting females. 3) We found no evidence that O. lignaria females avoided any level of imidacloprid contamination, even at the highest residue level (1,000 ppb) in both the experiments, which may have implications for risk. The in situ nesting methodology developed in this study has future applications for research on soil or pollen preferences of cavity nesting Osmia species, and potential for breeding of O. lignaria in laboratory.

© The Author(s) 2021. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.
Christine Cairns Fortuin and Kamal J. K. Gandhi "Mason Bees (Hymenoptera: Megachilidae) Exhibit No Avoidance of Imidacloprid-Treated Soils," Environmental Entomology 50(6), 1438-1445, (20 August 2021). https://doi.org/10.1093/ee/nvab083
Received: 29 March 2021; Accepted: 28 July 2021; Published: 20 August 2021

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choice experiment
nest material
Osmia lignaria
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