<div>Background: The prime intention of this research work was to assess the effect of synthetic insecticides and bio-pesticide against natural enemies of aphid, Lipaphis erysimi (Kalt.), mainly ladybird beetle Coccinella septumpunctata (Linnaeus) and syrphid fly, Ischiodon scutellaris (Fabricius) in mustard was evaluated.&nbsp; 
 
Methods: The field experiment was conducted at Student Research Farm, Department of Entomology, CSAUA and T Kanpur during Rabi season of 2013-14 and 2014-15. Experiment conducted in Randomized block design with three replication and eight treatments. Imidacloprid, deltamethrin, spinosad, fipronil, thiamethoxam, Metarhizium anisopliae and Beauveria bassiana were tested against natural enemies and available population of natural enemies of aphid were recorded before 1 day and after 3, 5, 7 and 14 days of spray application. M. anisopliae and B. bassiana were the most effective with less toxicity against Ladybird beetle and syrphid fly by continuously increasing population after application. Though all the tested chemical insecticides were found toxic to the lady bird beetle and syrphid fly larvae, imidacloprid and thiamethoxam were found relatively safer to other insecticides by recording less mortality after 14 days of spraying during two years testing period. &nbsp; 
 
Result: M. anisopliae, B. bassiana, imidacloprid and thiamethoxam may be used for the management of insect pests because of their less toxicity to beneficial insects.</div>

<div style="text-align:justify">Synthetic Insecticides and Bio-pesticide Affect Natural Enemies of Aphid (Lipaphis erysimi Kalt) in Mustard&nbsp;</div>