Particle drift simulation from mesotrione and rimsulfuron plus thifensulfuron-methyl mixture through two nozzle types to field and vegetable crops

Potential for off-target movements follows every herbicide application. Because the launch of acetolactate synthase (ALS)- and 4-hydroxyphenylpyruvate dioxygenase (HPPD)-inhibiting herbicide-tolerant crops will increase the treated area, there is a need to assess the possible negative consequences of any particle drift from those herbicides. Drift happens with every pesticide application, requiring mitigation. Various factors influence drift. Some, such as nozzle type, working pressure, and boom height, can be managed. Others, such as wind, are not easy to manage. In our study, an herbicide tank mixture of mesotrione with rimsulfuron plus thifensulfuron-methyl was sprayed in a low-speed wind tunnel to simulate drift. The airspeed was set at 4.4 m s^-1, representing the labeled upper limit for applications. The herbicide solution was sprayed through XR110015 and TTI110015 nozzles. Eight crops were exposed to herbicide drift treatments and biomass data were collected. Droplet size spectra and tracer depositions were evaluated. Tracer deposition was on average threefold higher in all downwind distances (0.5, 1, 2, 3, 4, 6, 9, and 12 m) from the XR nozzle in comparison to the TTI nozzle. As a consequence, greater biomass reduction was recorded for applications with the XR compared to the TTI nozzle from 1 to 12 m downwind. At 12-m distance, biomass was decreased by 7-78% using XR nozzle while 1-27% using the TTI nozzle. Because drift can injure crops, it is very important to mitigate drift from application of formulations containing mesotrione and rimsulfuron plus thifensulfuron-methyl in combination. This can be done by selecting the appropriate nozzle and ensuring optimal distances between crops.

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 μm) compared to the ULDM (930.3 μm), TDXL-D (872.9 μm), and TTI nozzles (854.8 μm). The premix formulation had greater D_V0.5 (971.0 μm) compared to the tankmix (922.3 μm). 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. © 2021 Society of Chemical Industry.