Effect on biology of jute indigo caterpillar, Spodoptera litura (Fabricius) under five different constant temperatures

Effect of six constant temperatures viz., 18±1 °C, 21±1 °C, 24±1 °C, 27±1 °C, 30±1 °C and 33±1 °C on growth, development and survival of Spodoptera litura (Fabricius). Development rate of egg, larvae, pupae and adult gradually increased with increase in temperature, while the total development period decreased. The total life span of the insect decreased from 64.19±2.86 days at 18±1 °C to 27.18±1.64 days at 33±1 °C. The egg hatchability, larvae reaching 4th instar, total pupation and adult emergence were maximum at 27±1 °C and it decreased with the increase or decrease in the temperature. Developmental thresholds were determined to be 11.93, 10.68, 9.54 and 10.98 for egg, larvae, pupae and adults respectively with corresponding thermal constants being 34.48, 344.82, 163.93 and 107.52 degree days. Thermal constant to complete a generation was found to be 650.70 DD. These estimated thermal thresholds and degree days could be used to predict the S. litura activity in the field for their effective management through pest forecasting and time of insecticide application.