Glufosinate‑P Herbicide Disrupts Gut Microbiota and Metabolism, Driving Osmia excavata Population Decline

Solitary bees face overlooked herbicide risks. Osmia
excavata, a key early spring solitary bee, is especially
vulnerable during soil-contact nesting, which coincides with peak
herbicide use. We evaluated sublethal effects of glufosinate-P on O. excavata. After 15-day exposure, 5–50 mg/L
glufosinate-P significantly reduced survival (by 25.00–57.50%)
and food intake (by 24.95–49.95%; P < 0.05).
High-dose (50 mg/L) exposure disrupted gut microbiota, increasing
pathogenic Serratia marcescens and
depleting beneficial microbes. Metabolomics showed systemic dysfunction,
with a 32.18% reduction in glutamate disrupting amino acid metabolism,
biosynthesis and nutrient transport, closely associated with microbiota
shifts. The dual stressors of pathogen enrichment and metabolic paralysis
compromised individual fitness and colony resilience, establishing
a mechanistic pathway for population decline. Glutamate depletion
emerged as a key biomarker connecting glufosinate-P exposure to systemic
metabolic disturbance in nontarget pollinators. These findings underscore
the need to reassess herbicide practices and integrate solitary bees
into pesticide risk assessments to protect pollination.