Effect of elevated co2 and temperatures on thermal requirement and thermal constants of beet armyworm, Spodoptera exigua (Noctuidae: Lepidoptera) on chickpea

Abstract

The objective of this study was to examine the development of beet armyworm, Spodoptera exigua (Noctuidae: Lepidoptera) at six temperatures (20, 25, 27, 30, 33 and 35 °C) and to estimate temperature thresholds and thermal constants for the forecasting models based on heat accumulation units, which could be developed for use in forecasting. The developmental periods of different stages of S. exigua were reduced with increases in temperature from 20 to 35 °C under both ambient and elevated CO2 conditions. The lower development threshold for egg, larva, pupa, adult and total development period required 11.57, 10.72, 9.05, 6.97 and 10.24 oC under eCO2 conditions, whereas it was 11.61, 10.43, 10.49, 6.15 and 9.83 oC under aCO2 conditions, respectively. The thermal requirement of S. exigua from egg to adult (total development period) was found to be 588.24 degree days under eCO2 conditions as against 555.56 degree days under aCO2 conditions. These estimated temperature thresholds and degree days can be predict the occurrence, number of generations and population dynamics of S. exigua.