Bionomics of mustard aphid Lipaphis erysimi (Kalt.) was surveyed and studied both in field crops and experimental fields sown with Brassica compestris var. sarson in the Tekari and konch area of Gaya district seasonal activity, host range and nature and extent of damage caused by aphid pests were evaluated and studied during September to April of two crop seasons of mustard crop i.e. 2013-2015.