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Native bees are in decline as many species are sensitive to habitat loss, climate change, and non-target exposure to synthetic pesticides. Recent laboratory and semi-field assessments of pesticide impacts on bees have focused on neonicotinoid insecticides. However, field studies evaluating influences of neonicotinoid seed treatments on native bee communities of North America are absent from the literature. On four Conservation Areas of Missouri, we sampled row-cropped (treated, n = 15) and reference (untreated, n = 9) agricultural fields, and their surrounding field margins for neonicotinoids in soil and non-target vegetation (i.e., native wildflowers). Wildflowers were further collected and screened for the presence of fungicides. Concurrently, we sampled native bees over three discrete time points throughout the agricultural growing season to assess potential impacts of seed treatment use on local bee populations over time. Neonicotinoids were detected in 87% to 100% of treated field soils and 22% to 56% of reference field soils. In adjacent field margin soils, quantifiable concentrations were measured near treated (53% to 93% detection) and untreated fields (33% to 56% detection). Fungicides were detected in < 40% of wildflowers, whereas neonicotinoids were rarely detected in field margin vegetation (< 7%). Neonicotinoid concentrations in margin soils were negatively associated with native bee richness (beta = -0.21, P < 0.05). Field margins with a combination of greater neonicotinoid concentrations in soil and fungicides in wildflowers also contained fewer wild bee species (beta = -0.21, P < 0.001). By comparison, bee abundance was positively influenced by the number of wildflower species in bloom with no apparent impact of pesticides. Results of this study indicate that neonicotinoids in soil are a potential route of exposure for pollinator communities, specifically ground-nesting species. Importantly, native bee richness in non-target field margins may be negatively affected by the use of neonicotinoid seed treatments in agroecosystems. ; Missouri Department of Conservation; Missouri Cooperative Fish and Wildlife Research Unit; USDA-NIFAUnited States Department of Agriculture (USDA) [MO-HANR0007]; MDC; University of Missouri; U.S. Fish and Wildlife ServiceUS Fish & Wildlife Service; U.S. Geological SurveyUnited States Geological Survey; Wildlife Management Institute; USDA-NIFA through Multi-State Working Group W3045 [MO-MSNR0002] ; We are grateful for the analytical support provided by the Water Sciences Laboratory at the University of Nebraska-Lincoln and the USDA AMS National Science Lab in Gastonia, NC. We thank W. Boys, D. Corcoran, G. Graells, K. Kuechle, J. Piercefield, and A. Wilcox for their involvement with field data collection. Special thanks to the MDC Area Managers for their willing participation in this research: D. Bryant, C. Freeman, C. Smith, and N. Walker. We appreciate M. Arduser (MDC retired) and J. LaRose for assisting in more challenging bee identification. Our appreciation to N. Michel (National Audubon Society) for statistical troubleshooting. We thank C. Otto (USGS) and three other anonymous reviewers for their valuable insights into development of this paper. This work was funded through a cooperative agreement with the Missouri Department of Conservation in collaboration with L. Webb and K. Goyne. Partial support was also provided by Missouri Cooperative Fish and Wildlife Research Unit and USDA-NIFA through Hatch funding (MO-HANR0007) and Multi-State Working Group W3045 (MO-MSNR0002). The Missouri Cooperative Fish and Wildlife Research Unit is jointly sponsored by the MDC, the University of Missouri, the U.S. Fish and Wildlife Service, the U.S. Geological Survey, and the Wildlife Management Institute. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. ; Public domain authored by a U.S. government employee

Throughout the Midwestern US, many public lands set aside for conservation engage in management activities (e.g., agriculture) that may act as stressors on wild bee populations. Several studies have investigated how wild bees respond to large-scale agriculture production; however, there has been limited assessment of how wild bees may be impacted by agricultural activity on public lands or how local variables may influence bee communities in these same areas. In this study, we assessed the abundance and richness of wild bee floral and nesting guilds at 30 agricultural field margins located on five Conservation Areas in Missouri. Generally, regardless of guild, bee abundance and richness was greater in field margins with more floral diversity and taller vegetation. Bee guilds responded negatively to agricultural production in Conservation Areas with fewer soil- and cavity-nesting bees collected in margins adjacent to annually cropped fields. Although fewer diet specialists were collected, specialist bee abundance and richness was greater in margins near fields that were uncropped (i.e., vegetated, but not row-cropped) during the previous year. Overall, the percentage of trees and shrubs within 800 m of study fields (i.e., "woodland") was negatively associated with abundance and richness of bees, but specifically, reduced richness of soil-nesters and diet specialists. Our findings indicate agricultural management activities on public lands may lead to decreased abundance and richness of wild bee guilds. If public lands are to be managed for species diversity, including wild bees, maintaining diverse plant communities with taller vegetation (>100 cm) near cultivated fields and/or modifying agricultural production practices on public lands may greatly improve the conservation of local bee communities. (C) 2019 The Authors. Published by Elsevier B.V. ; Missouri Department of Conservation (MDC); Missouri Cooperative Fish and Wildlife Research Unit; USDA-NIFAUnited States Department of Agriculture (USDA) [MO-HANR0007]; Multi-State Working Group W3045 [MOMSNR0002]; MDC; University of Missouri; U.S. Fish and Wildlife ServiceUS Fish & Wildlife Service; U.S. Geological SurveyUnited States Geological Survey; Wildlife Management Institute ; Special thanks to the MDC Conservation Area managers and biologists for their willing participation in this research: B. Anderson, D. Bryant, J. Demand, B. Diekmann, C. Freeman, A. Pearson, C. Smith, and N. Walker. We appreciate W. Boys, D. Corcoran, G. Graells, K. Kuechle, J. Piercefield, and A. Wilcox for their assistance in field data collection. Thank you to M. Arduser for his willingness to consult on identification of more challenging bee species. We thank M. Vandever (USGS) for his insightful reviewof our manuscript and the two other anonymous reviewers for their time and comments into strengthening this paper. This work was funded through a cooperative agreement with the Missouri Department of Conservation (MDC) in collaboration with L. Webb and K. Goyne. Partial support was also provided by Missouri Cooperative Fish and Wildlife Research Unit and USDA-NIFA through Hatch funding (MO-HANR0007) and Multi-State Working Group W3045 (MOMSNR0002). The Missouri Cooperative Fish and Wildlife Research Unit is jointly sponsored by the MDC, the University of Missouri, the U.S. Fish and Wildlife Service, the U.S. Geological Survey, and the Wildlife Management Institute. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. ; Public domain authored by a U.S. government employee

Wild bees support global agroecosystems via pollination of agricultural crops and maintaining diverse plant communities. However, with an increased reliance on pesticides to enhance crop production, wild bee communities may inadvertently be affected through exposure to chemical residues. Laboratory and semi-field studies have demonstrated lethal and sublethal effects of neonicotinoids on limited genera (e.g., Apis, Bombus, Megachile), yet full field studies evaluating impacts to wild bee communities remain limited. Here, we conducted a two-year field study to assess whether neonicotinoid seed treatment and presence in environmental media (e.g., soil, flowers) influenced bee nest and diet guild abundance and richness. In 2017 and 2018, we planted 23 Missouri agricultural fields to soybeans (Glycine max) using one of three seed treatments: untreated (no insecticide), treated (imidadoprid), or previously-treated (untreated, but neonicotinoid use prior to 2017). During both years, wild bees were collected in study field margins monthly (May to September) in tandem with soil and flowers from fields and field margins that were analyzed for neonicotinoid residues. Insecticide presence in soils and flowers varied over the study with neonicotinoids infrequently detected in both years within margin flowers (0%), soybean flowers (<1%), margin soils (<8%), and field soils (similar to 39%). Wild bee abundance and species richness were not significantly different among field treatments. In contrast, neonicotinoid presence in field soils was associated with significantly lower richness (ground- and aboveground-nesting, diet generalists) of wild bee guilds. Our findings support that soil remains an underexplored route of exposure and long-term persistence of neonicotinoids in field soils may lead to reduced diversity in regional bee communities. Future reduction or elimination of neonicotinoid seed treatment use on areas managed for wildlife may facilitate conservation goals to sustain viable, diverse wild bee populations. Published by Elsevier B.V. ; Missouri Department of Conservation (MDC); USDA-NIFAUnited States Department of Agriculture (USDA) [MO-HANR0007]; MultiState Working Group W3045 [MOMSNR0002]; MDC; University of Missouri; U.S. Fish and Wildlife ServiceUS Fish & Wildlife Service; U.S. Geological SurveyUnited States Geological Survey; Wildlife Management Institute ; Published version ; Thank you to M. Arduser, T. Christensen, O. Hannig, K. Kuechle, R. Owen, and J. Piercefield for assistance in field data collection or bee identification. We appreciate the support and involvement of MDC Area Managers, biologists, and staff. Special thanks to A. HarmonThreatt and two anonymous reviewers for their insightful comments to help strengthen the manuscript. This work was funded through a cooperative agreement with the Missouri Department of Conservation (MDC) . Partial support was also provided to KG by USDA-NIFA through Hatch funding (MO-HANR0007) and MultiState Working Group W3045 (MOMSNR0002) . The Missouri Cooperative Fish and Wildlife Research Unit is jointly sponsored by MDC, the University of Missouri, the U.S. Fish and Wildlife Service, the U.S. Geological Survey, and the Wildlife Management Institute. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

Pesticide exposure is a growing global concern for pollinator conservation. While most current pesticide studies have specifically focused on the impacts of neonicotinoid insecticides toward honeybees and some native bee species, wild pollinators may be exposed to a broader range of agrochemicals. In 2016 and 2017 we collected a total of 637 wild bees and butterflies from the margins of cultivated agricultural fields situated on five Conservation Areas in mid-northern Missouri. Pollinators were composited by individual genera (90 samples) and whole tissues were then analyzed for the presence of 168 pesticides and degradation products. At least one pesticide was detected (% frequency) in the following wild bee genera: Bombus (96%), Eucera (75%), Melissodes (73%), Pnlothrix (50%), Xylocopa (50%), and Megachile ( 17%). Similarly, at least one pesticide was detected in the following lepidopteran genera: Hemaris (100%), Hylephila (75%), Danaus (60%), and Colitis (50%). Active ingredients detected in >2% of overall pollinator samples were as follows: metolachlor (24%), tebuconazole (22%), atrazine (18%), iinidadoprid desnitro (13%), bifenthrin (9%), flumetralin (9%), p, p'-DDD (6%), tebupirimfos (4%), Iludioxonil (4%), flutriafol (3%), cyproconazole (2%), and oxacliazon (2%). Concentrations of individual pesticides ranged from 2 to 174 ng/g. Results of this pilot field study indicate that wild pollinators arc exposed to and are potentially bioaccumulating a wide variety of pesticides in addition to neonicotinoids. Here, we provide evidence that wild bee and butterfly genera may face exposure to a wide range of insecticides, fungicides, and herbicides despite being collected from areas managed for conservation. Therefore, even with the presence of extensive habitat, minimal agricultural activity on Conservation Areas may expose pollinators to a range of pesticides. Published by Elsevier B.V. ; MDC; Missouri Cooperative Fish and Wildlife Research Unit; USDA-NIFAUnited States Department of Agriculture (USDA) [MO-HANR0007]; Multi-State Working Group W3045 [MOMSNR0002]; University of Missouri; U.S. Fish and Wildlife ServiceUS Fish & Wildlife Service; U.S. Geological SurveyUnited States Geological Survey; Wildlife Management Institute; USGS Toxic Substances Hydrology ProgramUnited States Geological Survey ; We thank the following individuals for assistance in field data collection and lab sample preparation: W. Boys, K. Kuechle, J. Murray, and J. Piercefield. Thank you to C. Sanders, M. McWayne and M. De Parsia who processed the pollinators for pesticide analysis. Special thanks to all of the Missouri Department of Conservation (MDC) Area Managers, biologists, and their staff for their willingness to support this research: B. Anderson, D. Bryant, J. Demand, B. Diekmann, C. Freeman, A. Pearson, C. Smith, and N. Walker. This work was funded through a cooperative agreement with the MDC in collaboration with L. Webb and K. Goyne. Partial support was also provided by the Missouri Cooperative Fish and Wildlife Research Unit and USDA-NIFA through Hatch funding (MO-HANR0007) and Multi-State Working Group W3045 (MOMSNR0002). The Missouri Cooperative Fish and Wildlife Research Unit is jointly sponsored by MDC, the University of Missouri, the U.S. Fish and Wildlife Service, the U.S. Geological Survey, and theWildlife Management Institute. Pesticide residue analysis was supported by the USGS Toxic Substances Hydrology Program. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. ; Public domain authored by a U.S. government employee