Selected Demographic Data of the Bird Cherry-Oat Aphid, Rhopalosiphum padi L. on Corn, Zea mays L. at Different Temperatures

The bird cherry-oat aphid, Rhopalosiphum padi (L.) (Hemiptera: Aphididae), is a serious pest of Poaceae plants, especially wheat and corn, in the world and in Iran. In this study, the demographic parameters of R. padi were determined at seven constant temperatures (8.5, 15, 20, 25, 27.5, 29 and 31±0.5 °C), 65±5% RH, and 14:10 (L: D) photoperiods on Zea mays L., KSC704 cultivar. The total lifespan, from birth to death, decreased with increasing the temperature from 8.5 to 29 °C, but the nymphal stage duration increased a little at 29 °C. The highest value of life expectancy (ex) was observed at 8.5 °C and at 31 °C, the nymphs died before reaching the adult phase. The percentage of survival for nymphal stages was highest at 15 and 25 °C, and the net reproductive rate (R0=23.671 female/generation) had the highest value at 15 °C. The intrinsic rate of increase (rm) and the finite rates of increase (λ) increased at the temperature interval of 8.5 to 25 °C. At this range, the doubling time (DT) and the mean generation time (T) decreased as the temperature increased. According to the highest value of rm (0.22 day-1) and λ (1.134day-1) and also the lower value of T (9.095 d) and DT (2.16 d), the temperature of 25 °C was determined as the optimal temperature and the data showed that the proper temperature range for growth and reproduction of this aphid was between 15-25 °C. The effect of temperature on reproduction, especially the intrinsic rate of increase (rm), of R. padi would be useful for predicting its long-term population fluctuation over several generations and establishing integrated pest management (IPM) strategies against this pest.