Evaluation of isoxaflutole and thiencarbazone–methyl for the management of itchgrass Rottboellia cochinchinensis (Lour.) Clayton in maize

AbstractItchgrass Rottboellia cochinchinensis (Lour.) Clayton is a highly invasive annual grass, ranked among the world’s most troublesome weeds. In Karnataka, and in many other states of India, it poses a serious threat to maize and other crops across major maize-growing regions. As most herbicides have shown limited efficacy against this weed, a field study was conducted with an objective to study the effect of isoxaflutole + thiencarbazone-methyl for the management of R. cochinchinensis in maize. It was conducted during Kharif 2023 and 2024 at a farmer’s field in Pura village, Manchenahalli hobli, Gauribidanur taluk, Chikkaballapura district, Karnataka. The evaluated weed management options include: the pre- emergence application (PE) and early post-emergence application (EPoE) of isoxaflutole 225 g/L + thiencarbazone-methyl 90 g/L SC (isoxaflutole + thiencarbazone-methyl) (ready- mix) 73.12+29.25 and 90+36 g/ha, atrazine 50% WP (atrazine) 1000 g/ha PE, and topramezone 336 g/L w/v SC (topramezone) 33.6 g/ha + adjuvant 2 ml/L of water EPoE, hand weeded thrice at 20, 40, and 60 days after seeding (DAS) (weed-free) and an untreated control. The isoxaflutole + thiencarbazone- methyl provided superior control of R. cochinchinensis and most associated weed species, except Cyperus rotundus. Isoxaflutole + thiencarbazone-methyl (ready- mix) at both 73.12+29.25 and 90+36 g/ha PE and EPoE, consistently achieved the highest weed control efficiency, maximum maize grain and straw yield, and the lowest weed index demonstrating that it has a highly effective and promising option for managing R. cochinchinensis in maize.