Temperature dependent survivorship and development of Helicoverpa armigera (Hubner) (Lepidoptera-Noctuidae) on chickpea

Abstract Effect of constant temperatures (14°, 16°, 18°, 20°, 22°, 25°, 27°, 30°, 32°, 35° and 36°C) on demography and development ofHelicoverpa armigerawas evaluated under laboratory conditions (with 65% RH and 14L:10D h) on chickpea. Potential fecundity (pf) was significantly reduced to 86 females/female/generation at 35ºC compared to 532 at 27ºC. Intrinsic rate of increase (rm) was minimum (0.0191 females/female/day) at 14ºC and maximum (0.0489) at 30ºC. Estimate of linear regression model showed that lower temperature threshold (Tmin) of egg stage was 7.71ºC. Values of Tminfor 1st, 2nd, 3rd, 4th, 5th and 6th instar were estimated as 4.97º, 10.52º, 4.67º, 4.44º, 5.74º and 4.19ºC, respectively. Total heat requirement for embryonic development was 74.07ºC-day. Degree day (DD) estimated by Arnold method showed that 542.75 DD was required by immature stage ofH. armigerato complete its life cycle at 36ºC. Estimates of cubic polynomial model showed that lower temperature threshold (Tmin) required for embryonic development was 8.47ºC and upper temperature threshold (Tmax) was 38.83ºC. Tminrequired for development of 1st, 2nd, 3rd, 4th, 5th and 6th instar was 9.68º, 8.93º, 10.11º, 12.05º, 9.12º and 10.47ºC, respectively and Tmaxwas 40.84º, 36.53º, 37.38º, 41.59º, 39.53º and 40.26ºC, respectively. It is concluded that pf was maximum at 27ºC while rmat 30ºC. Development ofH. armigeraincreased with increase in temperature and optimum development occurred at the range of 27º to 30ºC. Moreover, demographic parameters ofH. armigeraalong with the thermal effect can be used to develop the models of population growth and prediction.