Bioefficacy and Economics of Some Insecticides and Post Bloom Sprays against Mustard Aphid, Lipaphis erysimi

The bioefficacy of some insecticides on mustard against mustard aphid, Lipaphis erysimi was studied during pre-bloom and post-bloom stage of the crop and it was revealed that soil application of carbofuran followed by post-bloom spray of cypermethrin (T₂) at 28 days after the first treatment and soil application of imidacloprid followed by post bloom spray of cypermethrin (T₆) at 28 days after the former treatment proved to be the most effective treatments during both years (2010 and 2011). There was complete control of the aphids L. erysimi after 35, 42 and 49 days after the pre-bloom treatment as its population was reduced to zero during both the years under study. The treatment involving application of carbofuran followed by post-bloom spray of cypermethrin (T₂) resulted in significantly higher seed yield of 12.5 and 14.1 q/ha during 2010 and 2011, respectively, whereas the seed yield in control plots during the respective years was significantly lower (6.4 and 7.9 q/ha) than all the treatments. The pre-bloom treatment of carbosulfan followed by post bloom spray of cypermethrin (T₄) emerged as the most economic treatment during both the years with B: C ratio of 3.7: 1 and 4.9: 1.