Department of Entomology, Dr. Y.S. Parmar University of Horticulture and Forestry, Solan-173 230, 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, H.P. (India).
The key-factors in fluctuation of Pieris brassicae (L.) (Lepidoptera: Pieridae) population were determined with the help of life tables in cabbage and cauliflower at Solan (1200 m amsl), Himachal Pradesh. There was 60.5 and 66.7 per cent mortality in different developmental stages during the first generation (March-April) in cabbage and cauliflower ecosystem, respectively. The corresponding mortality in the second generation (April-May) was 73.1 and 75.5 per cent. The major mortality factors in larval stage-I (first and second instar) and III (fourth and fifth instar) were rain and a parasitoid, Apanteles glomeratus (L.) in the two generations, respectively. The generation survival (SG) was more in the first than the second generation in both the crop ecosystems. Value of the 'trend index' (I) was more than unity for the first generation (1.654 on cabbage, 1.417 on cauliflower) indicating the mortality factors operating were not effective to set in a declining trend in P. brassicae population but could do so in the second generation.
