Seasonal incidence of mustard aphid, Lipaphis erysimi (Kalt.) and associated natural enemies on mustard crop were studied during 2009-2010. The first incidence of pest was observed in the second week of November 2009 (0.47 aphids on 3 leaves/plant) which reached its peak in the last week of December (70.48 aphids/2 cm central shoot/plant). Complete disappearance of pest was recorded during the second week of February when the crop was at maturity stage. The incidence of natural encmics coincided with the incidence of aphid (second week of November 2009). The natural enemies observed on mustard aphid colonies included four species of coccinellids, one syrphid and one Diaereliella rapae.Coccinellids were present throughout the cropping season of the mustard crop whereas, syrphid and D. rapae during the reproductive stage. Studies on the biology and feeding potential of Coccinella septempunctata Linn. was carried out under laboratory conditions. The fecundity of beetle was 239.9 � 80.11eggs / female. The mean incubation period, larval period, pupal period, adult longevity and total life span were 4.4 � 0.82 days, 23.25 � 4.28 days, 7 � 0.85 days, 57.65 � 8.62 and 104 � 21 days, respectively. The average number of aphids consumed by 1st, 2nd, 3rd and 4th instars larva of C. septempunctata were 3.84 � 0.9, 10.53 � 1.53,27.34 � 2.18 and 34.05 � 2.64 aphids/day, respectively. Among the larval stages, highest voracity was observed in 4th instar. Adult females were found to be more voracious (48.6 � 3.12 aphids/day) as compared to male (41.66 � 3.1 aphids/day). It is concluded that lady bird beetle could be a useful bioagent in controlling mustard aphid population especially during its peak infestation.