author(s)
Yogandar Sain, Rajendra Singh and Sushil Kumar

abstract
A field study was conducted on incidence of cabbage aphid, Lipaphis erysimi (Kalt.) in two different brassica spp. viz., Brassica oleracea and Brassica juncea during rabi season of 2012-2013 (Crop Research centre, (CRC) Sardar Vallabhbhai Patel university of Agriculture and technology, Modipuram, Meerut). The initial population of aphid appeared in first week of November (44 standard week) and reached its maximum level of 95.40 aphid plant^-1 during third week of December (50 standard week) when the temperature and relative humidity ranged from 20.57°C to 11.21°C and 73.71 to 37.42 per cent, respectively. The population of aphid was found to be decreased very fast during 5th and 6th standard week. The correlation study of aphid with abiotic factors revealed positive relationship with temperature and relative humidity during cropping season.