Efficacy of Tribenuron-methyl Applied Alone and Tank Mix Against Broadleaf Weeds of Wheat (Triticum aestivum L.)

Field and pot studies were carried out to evaluate the efficacy of tribenuron-methyl 75% PX (paste extruded) formulation used alone and tank mixed with grassy (field conditions) and broadleaf (screen house) herbicides during 2006–07 and 2007–08 at CCS Haryana Agricultural University, Hisar. Tribenuron 15 g/ha was effective against Chenopodium album under field conditions and provided 85–88% control. Increasing the dose from 15 to 30 g/ha or to 45 g/ha further increased control of C. album, but the effect was similar at higher rates. Adding a non-ionic surfactant (0.2%) increased the efficacy of tribenuron compared to no surfactant. 2,4-D ester/amine 500 g/ha or Sodium salt 1000 g/ha provided 100% control of C. album and the mortality was similar to premix of mesosulfuron+iodosulfuron (Atlantis) 21.6 and 14.4 g/ha, premix of sulfosulfuron+metsulfuron (Total) 16 g/ha, metsulfuron-methyl 4 g/ha or higher rates of tribenuron (26.25, 30 and 45 g/ha with and without surfactant). Tribenuron had no adverse effect on wheat upto 45 g/ha and no residual phytotoxicity was observed on mungbean or sorghum planted after wheat harvest. Effect of carfentrazone 20 g/ha and tribenuron 15 g/ha was similar against C. album but lower than other treatments. All broadleaf herbicides provided significantly higher yield compared to weedy plots, but were inferior to pre- or tank-mix applications of grassy and broadleaf herbicides. Atlantis 21.6 g/ha was phytotoxic to wheat and significantly checked plant growth and produced lower yield than 14.4 g/ha application rate. Tank mix applications of pinoxaden 45 g/ha and clodinafop 60 g/ha with tribenuron 15 g/ha produced highest yield and yield attributes of wheat. Under pot studies, tribenuron 15 g/ha, carfentrazone 20 g/ha, metsulfuron 4 g/ha, 2,4-D ester 250 g/ha and their tank mix combinations were compared with 2,4-D 500 g/ha against Anagallis arvensis, Asphodelus tenuifolius, Chenopodium album, C. murale, Lathyrus aphaca, Melilotus indica, Malva parviflora, Medicago denticulata, Rumex dentatus, R. spinosus, Silene conoidea, Sisymbrium irio and Vicia sativa. Tribenuron 15 g/ha provided 73 to 100% control of A. arvensis, A. tenuifolius, M. denticulata, V. sativa, C. murale, R. spinosus, R. dentatus, C. album, S. irio and S. conoidea, but it was not effective against M. parviflora and L. aphaca. Effect was also lower on M. indica, but tank mix applications with carfentrazone/2,4-D or metsulfuron improved its control by 15 to 25%. The overall weed mortality by tribenuron was similar to that of carfentrazone, but better than 2,4-D 250 g/ha, though the effect was significantly less than metsulfuron or 2,4-D 500 g/ha. Tank mixing of carfentrazone with metsulfuron inflicted maximum weed mortality (data averaged over species), but it was statistically similar to all other mixtures except carfentrazone plus 2,4-D 250 g/ha which has significantly less weed mortality. Similar trend was recorded in fresh weight accumulation by weeds with different treatments. L. aphaca and M. parviflora were most difficult-to-control weeds, whereas S. conoidea and S. irio were most susceptible weeds (data averaged over herbicide treatments). Tribenuron 15 g/ha had no significant edge over metsulfuron 4 g/ha against any of the test species in the screen house, though in tank mix applications with pinoxaden and clodinafop it produced similar yield compared to recommended field herbicides, with the advantage of no residual toxicity on succeeding sensitive crops.