Field experiment was conducted during the kharif (wet) season of 2014 and 2015 in the farmer’s field of village Binuria, Sriniketan, Birbhum, West Bengal with blackgram variety ‘WBU-108’to study the effect of imazethapyr and other herbicides on growth of composite weed flora and productivity of kharif blackgram. The experiment comprising of eight treatments was laid out in a randomized block design with three replications. From the experimental findings it revealed that Digitaria sanguinalis among the grasses; Cyperus iria among the sedges and Ludwigia parviflora and Croton bonplandianum among the broadleaved weeds were predominant throughout the cropping period. Higher doses of imazethapyr (75, 100 and 125 g/ha) applied at 20 DAS effectively controlled the complex weed flora in blackgram at 45 DAS. Yield reduction in kharif blackgram due to weed infestation was to the tune of 26-29%. Lower values of weed density, total weed dry weight and higher values of weed control efficiency and yield of blackgram were registered with post emergent application of imazethapyr at 75 g/ha at 20 DAS which was followed by imazethapyr at 100 g/ha at 20 DAS. These treatments may be recommended for managing composite weed flora and obtaining higher yield of kharif blackgram in the lateritic belt of West Bengal, India.