The results of laboratory studies carried out during 2019-20 and 2020-21 to investigate the development of resistance towards recommended insecticides in mustard aphid, Lipaphis erysimi (Kalt.) are reported. Among different populations, Shri Muktsar Sahib population was the least susceptible with LC_(50) values ranging from 0.0011-0.0591 per cent whereas Ludhiana population was the most susceptible with LC_(50) values ranging from 0.0005-0.0238 per cent to all the insecticides tested. Among different insecticides, thiamethoxam with LC_(50) values ranging from 0.0005 to 0.0011 per cent showed maximum toxicity while dimethoate was found to be the least effective insecticide with LC_(50) values ranging from 0.0238 to 0.0591 per cent. Medium to high levels of resistance (16.2-74.2x) were observed towards dimethoate 30 EC, chlorpyriphos 20 EC and oxydemeton methyl 25 EC, whereas level of resistance towards thiamethoxam 25 WG was found to be very low (2.5-5.5x) in Punjab.
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