Evaluation of herbicidal activity and safety to rice of the combination of benzobicyclon and florpyrauxifen-benzyl

Benzobicyclon is a novel 4-hydroxyphenylpyruvate dioxygenase-inhibiting (HPPD) herbicide. The herbicidal activity and control efficacy of the combination of benzobicyclon and florpyrauxifen-benzyl were evaluated. Whole-plant dose-response experiments were conducted in greenhouse to evaluate the joint effect and the selectivity index of the mixtures between rice and weeds. Weed control efficacy and response of rice to the mixtures were also investigated in field experiments. The results of greenhouse experiments showed that the joint effect type was either additive or synergistic when benzobicyclon was mixed with florpyrauxifen-benzyl for the control of Echinochloa crus-galli, Leptochloa chinensis, Cyperus difformis and Monochoria vaginalis. When the mass ratio of benzobicyclon and florpyrauxifen-benzyl was 5:1, the weed control efficacy of the mixtures was higher than that treated only by benzobicyclon. The selectivity indexes between rice varieties and the tested weeds were in the range of 28.72-54.81, which demonstrated the safety of the mixtures to rice was improved compared with that of benzobicyclon and florpyrauxifen-benzyl used alone. The results of field efficacy test showed that the combination of benzobicyclon and florpyrauxifen-benzyl expanded the herbicidal spectrum. The fresh weight control effect against E. crus-galli,L. chinensis, C. difformis and Monochoria korsakowii was 93.4%-100% which was safe to rice. The recommended dosage applied in the field was 120 g a.i/hm² for benzobicyclon and 18 g a.i/hm² for florpyrauxifen-benzyl, and the control effect against weeds was between 97.1%-100%.