ORIGINAL ABSTRACT

South America has one of the highest rates of pesticide use worldwide; however, their impact on native bees remains poorly understood. Glyphosate has been shown to affect bees at field-realistic concentrations, but remains understudied in wild species. As this herbicide is the most widely used pesticide in Argentina, the present study aimed to evaluate the dynamics of glyphosate and its metabolite AMPA in the bumblebee Bombus pauloensis and environmental matrices across contrasting land uses -food horticulture (FH), ornamental horticulture (OP), organic agriculture (OA), and urban parks (UR)- during application (Appli) and post-application (Post Appli) periods (2021-2022). Concentrations in workers (females) and males (only Post Appli), flowers, and soils were determined by HPLC-MS/MS. Glyphosate was detected in 43% of samples. The maximum significant levels in workers and soils were found in OP during the Appli period (252.78 - 485.68 and 831.65 - 1728.07 ng/g, respectively); while the highest levels in males were found in FH (<LOD - 177.68 ng/g). In flowers, the maximum concentration was registered in OA during Post Appli (324.50 - 486.22 ng/g). AMPA was detected only in soils. Site and period significantly influenced contamination patterns. Glyphosate was rarely detected in UR and at the lowest concentrations. Levels found in bumblebees and flowers from the rural areas suggest active use and/or aerial drift, and fall within ranges reported to affect bumblebees. This study provides the first evidence of glyphosate exposure in native bees from a major horticultural belt in Argentina, suggesting similar scenarios may be occurring in comparable agroecosystems.