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In continuation for the search of appropriate weed control strategy for sugarcane field weeds at the Unilorin Sugar Research Institute (USRI), Ilorin located at 8o 030' N; 4o 32' E , Nigeria. Field trials were laid out in a randomized complete block design during 2012 and 2013 growing seasons to evaluate four herbicide formulations using different rates of application. In each of the trials, three-eyed budded setts of 7 months old sugarcane varieties were laid end-to-end on 6 ridges of 5 m long per plot in three replications. Terbuthylazine 500 SC and 90 WG were applied as pre-emergence herbicides while dicamba 480 SL and dicamba 70 SG as post emergence herbicides. The result shows that application of the above formulations did not significantly affect the emergence of sugarcane. The efficacy of pre-emergence application decreases from 4 week after application (WAA) while the efficacy of post-emergence increased to peak (8 WAA) and decreased gradually. The highest rates of application had the best efficacy across the assessment periods with no phytotoxic effects. This study concludes that, pre-emergence application of terbuthylazine 500 SC and 90WG at 4-5l/ha and 4-5kg/ha, respectively or post emergence application of dicamba 480 SL at 400-500ml/ha or dicamba 70 SG at 400- 500g/ha will effectively keep sugarcane field free of weeds for a long period during the vegetative phase of the crop which may translate into higher cane yield. The formulations evaluated could be an alternative weed control chemicals for sugarcane farmers or supplements to the existing sugarcane herbicides in the market.
Keywords: Herbicide formulation, terbuthylazine, dicamba, efficacy, sugarcane, cane yield