Indian Journal of Dryland Agricultural Research and Development

Groundnut bruchid, Caryedon serratus Olivier (Bruchidae: Coleoptera) is a primary insect pest of stored groundnut causing both quantitative and qualitative losses. Temperature dependent phenology models are valuable for understanding pest population dynamics and implementing IPM strategies in different agro-ecological zones. Development, survival and reproduction parameters of C. serratus at six constant temperature conditions (15, 20, 25, 27, 30 and 35°C) were investigated and further validated with data generated under fluctuating temperature conditions. The estimated lower developmental threshold temperatures were 8.76°C for eggs, 1.2°C for larvae, 0.8°C for pupae, 0.13°C for males and 0.5°C for females. Several nonlinear equations were fitted to each life stage to model the temperature-dependent population growth and species life history and finally compile an overall temperature-dependent pest phenology model using the Insect Life Cycle Modeling (ILCYM) software. The developed phenology model predicted temperature ranges between 25 and 30°C as favorable for C. serratus development, survival and reproduction. C. serratus population attained a maximum net reproductive rate (111.85-114.62 females/female/generation) and total fecundity (147.78-160.77 individuals/female/generation) at temperatures between 25 and 27°C. Mean length of generations decreased from 213.28 days at 15°C to 96.15 days at 35 °C. The maximum finite rate of increase (1.03-1.04 females/female/day) and shortest doubling time (17-19.04 days) were also observed at temperatures between 27 and 30°C. The simulation of phenology model at fluctuating temperatures indicated that C. serratus populations might potentially increase with a finite rate of 1.03 females/female/day with an average generation time of 123.84 days and a doubling time of 20.22 days.