Foliar Distribution of Seed-Applied Fluxapyroxad in Barley

Seed-applied fungicides play a crucial role in early-season disease management in cereals; however, their plant distribution and its effect on disease control remain poorly understood. This study examines the distribution of fluxapyroxad in seed-treated barley and its relationship with protection against Pyrenophora teres f. maculata. Using liquid chromatography–high-resolution mass spectrometry, fluxapyroxad concentrations were quantified at multiple growth stages in seed-treated barley. A progressive decrease in fungicide concentration was observed from the early emerging leaves to the younger ones. In older leaves, a pronounced base-to-tip enrichment pattern was detected, and this gradient was reflected in differential suppression of P. teres f. maculata, with the greatest protection occurring at leaf tips, where fungicide levels were up to 50-fold higher. These findings provide insights into how seed-applied fungicides, such as fluxapyroxad, behave in planta, supporting more strategic approaches to fungicide use that optimize crop protection, enhance input efficiency, and improve growers' outcomes.