Glyphosate Herbicides and Bee Health in Almond and Vineyard Systems

This study examines the impact of glyphosate-based herbicides, specifically Roundup products, on multiple bee species in almond orchards (Spain) and vineyards (Germany). Field experiments at 16 sites per country compared glyphosate-treated plots with mechanically weeded controls. Residues of glyphosate were detected in honey bees, Osmia bees, soil, and bee cell walls in Spain, and in bumble bee colonies and soil in Germany, but not in Osmia bees in Germany. Protein-to-lipid ratios in pollen were unaffected by treatment, sugar availability, or bee species. No significant effects were found on pollen quality, bumble bee worker or queen numbers, hive weight, or Varroa mite load in honey bees. However, bumble bee colony weight increased with Roundup treatment. Nectar sugar content influenced outcomes differently by region: in Germany, high sugar sites boosted bumble bee cocoon production in treated colonies, while in Spain, high sugar sites initially increased honey bee hive weight and flight activity. Varroa mite load rose more at high sugar sites in Spain. In Germany, more gynes emerged in Roundup colonies at low sugar sites. Results suggest no direct risk from glyphosate in plant-row applications, but formulation co-formulants may contribute to toxicity. The study underscores the importance of distinguishing between glyphosate and full herbicide formulations, and highlights potential sensitivity in young honey bees due to immature cuticles.