The studies on the relative occurrence and abundance of mustard aphid, Lipaphis erysimi (Kalt.) revealed that aphid appeared on leaves during 3rd week of January and on the inflorescences during 2nd week of February and continued up to harvesting on both the varieties. The peak populations (42.7) and (28.7) per leaf on Rainbow and Oscar varieties were recorded. Whereas, the peak populations (7.5) and (6.6) per inflorescences were recorded on these varieties. The higher mean population ranges (9.2 to 28.7) and (25.1 to 42.7) per leaf on Oscar and Rainbow and (3.9 to 6.6) and (2.3 to 7.6) per inflorescence were recorded from February 15 to March 5. The temperature range of 16.5 to $20.6^{circ}$, seems to have favored the pest multiplication. The predator species such as, green lacewing beetle, Chrysoperla carnea (Stephens), eleven-spotted ladybird beetle, Coccinella undecimpunctata (Linn.) and seven-spotted ladybird beetle, Coccinella septempunctata (Linn.) were recorded when the pest population of aphids was sufficiently developed on the canola varieties.