Department of Entomology, Himachal Pradesh Krishi Vishvavidyalaya, Palampur-176 062, Himachal Pradesh (India).
The population build-up of Lipaphis erysimi Kalt. infesting rapseed Brassica campestris var. brown sarson was studied during three years, i.e., 1989, 1990 and 1992. The abundance of L. erysimi was maximum during the last week of February. The mean maximum temperature during the peak population was l8.8°, 15.0° and 17.7°C; mean minimum temperature was 8.0°, 5.5° and 6.5°C; mean R.H. 32, 65 and 44%; and total rainfall 24.9, 67.8 and 2.5 mm in 1989, 1990 and 1992, respectively. Low rainfall, i.e., 3.3, 1.3 and 1.3 mm during the 3rd week of February 1989, 1990 and 1992, respectively. favoured the multiplication of L. erysimi in the 4th week of February. The sharp decline of the aphid population in the first week of March was attributed to rising temperature and production of alate forms coupled with crop maturity.
