Spray drift potential of dicamba plus S-metolachlor formulations

BACKGROUND Early-postemergence herbicide applications in the USA often include residual herbicides such as S-metolachlor to suppress late late-emerging Amaranthus spp. Although this practice benefits weed control, herbicide tankmixes can influence spray droplet size and drift potential during applications. The addition of S-metolachlor products to dicamba spray solutions generally decreases spray droplet size and increases spray drift potential. Advances in formulation technology fostered the development of products with reduced spray drift potential, especially for herbicide premixes containing multiple active ingredients. The objective of this study was to compare the drift potential of a novel dicamba plus S-metolachlor premix formulation (capsule suspension) against a tankmix containing dicamba (soluble liquid) and S-metolachlor (emulsifiable concentrate) using different venturi nozzles. RESULTS The MUG nozzle had greater D-V0.5 (1128.6 mu m) compared to the ULDM (930.3 mu m), TDXL-D (872.9 mu m), and TTI nozzles (854.8 mu m). The premix formulation had greater D-V0.5 (971.0 mu m) compared to the tankmix (922.3 mu m). Nozzle influenced spray drift deposition (P < 0.0001) and soybean biomass reduction (P = 0.0465). Herbicide formulation influenced spray drift deposition (P < 0.0001), and biomass reduction of soybean (P < 0.0001) and cotton (P = 0.0479). The novel capsule suspension formulation (premix) of dicamba plus S-metolachlor had reduced area under the drift curve (AUDC) (577.6) compared to the tankmix (913.7). Applications using the MUG nozzle reduced AUDC (459.9) compared to the other venturi nozzles (ranging from 677.4 to 1141.7). CONCLUSION Study results evidence that advances in pesticide formulation can improve pesticide drift mitigation.