Bispyribac-sodium, Herbicide resistance, Cyperus difformis, Resistant populations, Resistance management, Rice

The over-reliance on the acetolactate synthase-inhibiting herbicide bispyribac-sodium for broad-spectrum weed control in the rice-rice cropping system has led to an increase in the population of bispyribac-sodium resistant weeds. Cyperus difformis L. is one of the problematic and difficult-to-control weeds in the rice ecosystem with steady rise in the occurrence of bispyribac-sodium resistant populations. Therefore, to assist the rice farmers containing bispyribac-sodium resistant    C. difformis, alternate options were tested. A pot study was carried out during the rainy season of 2019 and 2020 at the ICAR-Directorate of Weed Research, Jabalpur to evaluate herbicides with different sites of action against susceptible and resistant populations of C. difformis. Fluorpyrauxifen-benzyl at 31.25 g/ha at 3-5 leaves stage of C. difformis caused 100% reduction, over untreated check, in C. difformis density, plant height, fresh and dry shoot biomass, and visible mortality at 21 days after treatment. Next best herbicide was bentazone at 960 g/ha (>90%). Similarly, chlorimuron + metsulfuron at 4 g/ha and 2,4-D amine salt at 500 g/ha also resulted in a substantial reduction in the growth of susceptible and resistant populations. It can be concluded that fluorpyrauxifen-benzyl at 31.25 g/ha could be a potential herbicide against C. difformis and to be evaluated under field situations to verify and confirm its efficacy.