Effects of Tank-Mix Adjuvants on Physicochemical Properties and Efficacy of Fluazifop- <i>p</i> -butyl against Three Weed Species

The hydrophobic waxy layer on grass leaves poses challenges for herbicide application by impeding wetting and deposition. The inclusion of appropriate tank-mix adjuvants with herbicides can overcome these problems. This study systematically evaluated the influence of five tank-mix adjuvants (Infiltrator, A-200, GY-Tmax, Velezia Pro, and Coerce) on the physicochemical properties, evaporation performance, and weed control efficacy of the herbicide fluazifop-p-butyl (FPB) against grass weeds, including Echinochloa crus-galli, Setaria viridis, and Digitaria sanguinalis. The critical micelle concentration (CMC) values of each adjuvant were identified by measuring the relationship between the surface tension of the solution and its concentration. At 2 CMC, the surface tension and contact angle reached their minimum values. A-200 demonstrated the best adhesion and wetting performance, followed by Coerce, GY-Tmax, Velezia Pro, and Infiltrator. Compared to the control without adjuvants, the wetting areas of A-200 and Coerce increased by 6.96- and 1.74-fold, respectively. At 25 °C, all adjuvants inhibited the evaporation of the solution. Even under a 20% reduction in herbicide, adjuvants such as A-200, Infiltrator, and GY-Tmax significantly enhanced the efficacy of FPB against weeds, achieving weed control effects comparable to those of the full herbicide dosage. This study demonstrates that appropriate adjuvants can improve the bioavailability of FPB, providing a theoretical basis for lowering herbicide application rates.