Efficacy of Sulfonylurea Herbicides alone and in Combination with Metribuzin for Control of Wild Canary Grass (Phalaris Minor Retz.) in Wheat (Triticum Aestivum L.) and their Residual Toxicity to Mungbean

Field trials were conducted during the rabi season of 2002–03 and 2003–04 at IARI Research Farm in New Delhi to study the efficacy of new sulfonylurea herbicides alone and in combinatton wiih metribuzin against wild canary grass (Phalaris minor Retz.) in wheat (Triticum aestivum L). Post-emergence application of chlorsulfuron @ 30 g ha⁻¹ metsulfuron-methyl @ 8 g ha⁻¹ ann metribuzin at 200 and 300 g ha⁻¹ alone and id combination with chlorsulfuron @ 15 g ha⁻¹ and metsulfuron-methyl @ 2 g ha⁻¹ provided effective control of P. minor and improved grain yield of wheat by 12.6–30.6% over weedy check. Application of chlorsulfuron @ 30 g ha⁻¹, metsulfuron-methyl @ 8 g ha⁻¹ and tank mix of chlorsulfuron + metribuzin (15 + 100 g ha⁻¹ and 15 + 200 g ha⁻¹) produced grain yield of wheat comparable with repeated hand weeding. Metribuzin @ 200 and 300 g ha⁻¹ and mixed wiih metsulfuron (2 g ha⁻¹) was found toxic to wheat and decreased grain yield by 17.1–21.9% compared with weed free condition. The highest weed control efficiency (82.2%) was achieved from metribuzin application @ 300 g ha⁻¹ followed by its tank mix application at lower dose of 200 g ha⁻¹ with chlorsulfuron (15 g ha⁻¹) and metsulfuron-methyl (2 g ha⁻¹). Bioassay studies showed the significant reduction in germination count, height, leaf area and fresh weight of mungbean due to the effect of metribuzin (300 and 200 g ha⁻¹) residues and its combination with metsulfuron (2 + 200 and 2 + 100 g ha⁻¹) followed by alone application of chlorsulfuron @ 30 g ha⁻¹ and metsulfuron @ 8 g ha⁻¹.