Effect of mowing timing and clipping collection practices on azoxystrobin distribution, persistence, and efficacy

Previous research suggests mowing practices following azoxystrobin application alter pest control and residue fate. Azoxystrobin, an acropetal penetrant quinone outside inhibitor fungicide, is commonly applied in turfgrass and other agricultural settings, protecting desired plants from fungal pathogens by inhibiting fungal growth. Field research was initiated in Raleigh, NC, and repeated in time to assess the effect of post-application mowing timing and clipping collection practices on azoxystrobin residue persistence in tall fescue (Schedonorus arundinaceus Schreb.). At trial initiation, azoxystrobin was applied at the maximum single application rate (0.61 kg ai ha⁻¹) to tall fescue plots. To determine the effect of initial mowing timing, plots were mowed (9.5 cm) at 0, 1, 2, 3, 7, or 14 days after application (DAA). To determine the effect of clipping removal, plots were mowed at 3, 10, and 17 DAA and clippings were either returned to the canopy or bagged and removed. Concurrently, soil cores (92 cm²) were collected at 3, 7, 14, and 21 DAA and then segmented into remaining aboveground vegetation and soil (0.0- to 2.5-cm depth) for residue analyses. Mowing timing affected azoxystrobin residue in the vegetation and in soil. When clippings were returned to the canopy, 5% more azoxystrobin was detected in the vegetation at 7 and 14 DAA. At 3 and 7 DAA, in the soil, returning clippings resulted in >3% more of the applied azoxystrobin compared to removing clippings. Data from this research may allow for extended fungicide intervals for brown patch suppression and demonstrate the importance of returning clipping to turf systems to retain azoxystrobin residues.