Population build-up of aphid complex (Lipaphis erysimi Kalt. and Brevicoryne brassicae Linn.) on rapeseed at Palampur, Himachal Pradesh (India)

The effect of abiotic factors on the population build-up of mustard aphid, Lipaphis erysimi Kaltenbach and cabbage aphid, Brevicoryne brassicae Linnaeus infesting rapeseed, Brassica campestris var. brown sarson (BSH-I), at Palampur (H.P.) was investigated. L. erysimi appeared in the first week of January and maximum aphid population was recorded in the last week of January, whereas B. brassicae appeared during the last week of January and maximum aphid was recorded during the first week of April. Temperature and relative humidity had no significant impact on the population build-up of both the species of aphids. Rainfall, however, caused a sudden reduction in the population.