Estimation and validation of developmental thresholds and thermal requirements for cotton pink bollworm Pectinophora gossypiella

Abstract

The developmental thresholds and thermal requirements of pink bollworm were estimated using laboratory data on its development at six constant temperatures from 15 °C to 38 °C. The results were validated using field data on male moth catches in sex pheromone traps baited with gossyplure recorded at Nagpur (Maharashtra) during 2018 for predicting the initiation of moth emergence and completion of generation events. The theoretical lower and upper threshold temperatures estimated using non–linear Sharpe and DeMichele model applied to mean development rates were: 14.17/35.43, 15.18/35.48, 11.00/35.48 and 13.40/35.50 °C, and the thermal requirements estimated as inverse of slope of linear regression were: 72.99, 285.71, 144.92 and 503.62° days for development of eggs, larvae, pupae and egg – adult emergence, respectively. Simulation of life table parameters provided reasonably closer estimates across the tested locations. The estimated lower and upper threshold temperatures accumulated the heat units (489.90–497.90) closer to the laboratory estimates (503.62 DD) and sensibly predicted the developmental events in pink bollworm with ±1.0 day error of margin under field conditions. The estimated thresholds and thermal requirements may help in comprehending seasonal dynamics of pink bollworm in relation to timings of developmental events like beginning and peaks of moth emergence, oviposition and egg hatching. This could facilitate in undertaking timely pest management actions such as insecticidal applications.