Department of Entomology, Dr. Yashwant Singh Parmar University of Horticulture and Forestry, Solan-1 73 230, Himachal Pradesh (India).
*A part of approved Ph.D. thesis submitted by A.K. Sood to Dr Y.S. Parmar University of Horticulture and Forestry, Solan, Himachal Pradesh (India).
Growth rate of Pieris brassicae (L.) was studied by developing fertility schedules on cabbage and cauliflower under laboratory conditions. On cabbage, population of P. brassicae multiplied 60.79 times over a generation time (T) of 43.2 days during the first generation (March-April) and 20.62 times in the second generation (April-May) occupying 34.2 days. The multiplication rate was lower on cauliflower in both the generations (56.53 and 14.64 times, respectively) at almost similar generation times. Intrinsic rate of increase (rm) was comparatively higher in insects reared on cabbage (0.095 and 0.098 in the first and second generations, respectively) than on cauliflower where rm value was 0.091 and 0.081 in the corresponding generations. Population on reaching a stable age-distribution comprised approximately 98.5% immature stages in the first and 98% in second generation on both the hosts. The daily mean temperature varied between 15–21°C in the first and 22–29°C in second generation while the relative humidity varied between 36–66% and 30–35% in the corrosponding generations.
