Population studies on the maize borer chilo partellus in the punjab india part 4 life tables for determining key mortality factors
Singh, B.; Dhaliwal, J.S.; Atwal, S.S.
Indian Journal of Ecology 4(1): 107-117
1977
ISSN/ISBN: 0304-5250 Document Number: 365172
The key factors determining fluctuations in the natural population of Chilo partellus were pinpointed by constructing life-tables and preparing budgets for the pre-monsoon, monsoon and post-monsoon periods. A positive trend index (1.15) indicates that the mortality factors operating during the pre-monsoon period were not effective in causing decline in the borer population. The maximum contribution towards generation mortality was of the first 2 larval instars and also owing to reduced fecundity and egg viability; the mortality agent was high temperature in both cases. Negative values of trend index during the monsoon (0.983) and post-monsoon (0.88) periods indicate that the mortality factors operating during these periods were effective in causing decline in the pest population. The maximum contribution towards generation mortality during the monsoon period was of the first 2 larval instars, rainfall being the mortality agent. Mortality among older larvae (3rd-5th instar) owing to cultural practices was the primary cause of reduced generation survival during the post-monsoon period. The natural enemies of C. partellus did not contribute substantially in regulating the pest population. The studies indicate that for minimizing the borer problem in the Punjab [India], manipulation of cultural practices is the appropriate approach.