Abstract
The development period was found to be 12 days in winter for I to IV instar, while it was only 5 days during spring and autumn. L. erysimi laid 52 viviparous offspring in winter and 26 each in other two seasons. Heavy infestation of L. erysimi on Brassica juncea showed stunted growth with leaf curling, crinkling, yellowing and eventually drying up of foliage and twigs. Mean monthly incidence of the mustard aphid during the crop season in November, December (2018) and January and February (2019) was 10.5, 45, 33.5 and 11 aphids/colony/cm2 during respective months. Examining the colony at different sites revealed that the population constitutes an average of 84.7% nymphs, 5.88% apterous and 2.42% alate individuals. The biochemical analysis of the aphid infested mustard leaf showed marginally higher levels of protein, carbohydrate, lipid and nitrogen than the normal leaf. The aphid's stylet penetration up to the phloem vessel has been shown through the transverse section of the infested leaf.
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