Bioefficacy and residues of imidacloprid in rapeseed-mustard

Imidacloprid formulations, 70 WS and 17.8 SL were applied as seed treatment @ 5 and 7 g/kg and as foliar spray @ 20 and 40 g a. i./ha, respectively, at flowering stage on mustard (Brassica campestris Linn.) to control the population of mustard aphid, Lipaphis erysimi Kalt. Both the treatments effectively controlled the aphid population when used as seed as well as foliar spray treatment. The highest cost: benefit ratio was found with lower doses (seed treatment 5 g/kg and foliar spray @ 20 g a. i./ha) in both the treatments and proved sufficient to optimize the yield of mustard crop. Residues of imidacloprid in mustard seed and soil were estimated on HPLC reverse phase system. Limit of detection (LOD) and limit of determination/quantification (LODe/LOQ) was calculated to be 0.003 and 0.01 mg/kg, respectively. Residues were below determination level (BDL) of 0.01 mg/kg in mustard seeds as well soil at harvest in both the treatments and doses.