Effect of acetolactate synthase inhibitor herbicides with 2, 4-D ethyl ester on complex weed flora in transplanted rice (Oryza sativa)

A field experiment was conducted during the rainy (kharif) seasons of 2015 and 2016 at Chiplima, Odisha, to evaluate acetolactate synthase herbicides with 2, 4-D ethyl ester for control of complex weed flora in transplanted rice (Oryza sativa L.). Post-emergence application of bispyribac sodium @ 20 g/ha, penoxsulam @ 22.5 g/ha, chlorimuron + metsulfuron @ 4 g/ha in sole as well as in combination with 2, 4-D ethyl ester @ 200 g/ha, effectively controlled Marsilea quadrifolia L., Ludwigia perennis L. and Ammnia baccifera L. Weeds reduced the grain yield of rice by 37.6%. Application of 2, 4-D ethyl ester alone was not effective against grassy weeds and aquatic fern (Marsilea quadrifolia L.) and bispyribac, penoxsulam and chlorimuron + metsulfuron were not much effective against Ammania baccifera and Cyperus difformis L. However, 2, 4-D ethyl ester in combination with bispyribac or penoxsulam was comparable to weed-free treatment in reducing the weed density. Tank-mix application of bispyribac sodium with 2, 4-D ethyl ester (20 + 200 g/ha) proved the most effective in minimizing Cyperus spp. and Ammania baccifera along with total control of Echinochloa spp., Marsilea quadrifolia and Ludwigia perennis. This treatment also resulted in the minimum total weed density (8.1/m²), biomass (11.1 g/m²) comparable to weedfree condition and the highest grain yield (5.97 t/ha), net returns (51.8 × 10³ /ha) and benefit: cost ratio (1.4).