Field evaluation of spray drift exposure and phytotoxic effects on non-target crops from UAV and conventional sprayers.

BACKGROUND: Spray drift is a major pathway for off-target pesticide exposure, posing risks to sensitive crops and ecosystems. Although numerous studies have evaluated drift from individual sprayer types, few have quantitatively linked field-measured drift deposition with crop injury across multiple application technologies. This study compared spray drift generated by unmanned aerial spraying systems (UASS), boom sprayers, and knapsack sprayers and quantified the resulting phytotoxic effects on sensitive crops. RESULTS: UASS equipped with the air-induction nozzle (IDK12001) consistently produced lower off-target drift deposition compared with conventional boom and knapsack sprayers, particularly under lower wind speed conditions. A strong relationship between drift deposition and crop injury was described by exponential decay model (R2 = 0.97). Drift exposure resulted in severe phytotoxic effects at near-field distances (1-3 m), where deposition exceeded approximately 20-30%. Green onion treated with nicosulfuron (H2) showed complete mortality (100%), whereas severe injury was observed in garlic exposed to florasulam (H1) and carfentrazone-ethyl (H3) (~95%) and in rapeseed exposed to nicosulfuron (H2) (~90%). Crop injury declined rapidly with distance and became negligible beyond 30-40 m. CONCLUSION: This study establishes a quantitative relationship between field-measured spray drift deposition and biological responses in sensitive crops. The findings provide a scientific basis for improved drift risk assessment, buffer zone determination, and selection of low-drift application technologies, thereby supporting safer and more sustainable pesticide application practices. © 2026 Society of Chemical Industry.