DIAPAUSE DYNAMICS IN PINK BOLLWORM (PECTINOPHORA GOSSYPIELLA) TRIGGERED BY EPISODES OF PHOTOPERIOD AND TEMPERATURE REGIMES

Abstract

Pink bollworm, Pectinophora gossypiella is considered as the most injurious insect-pest of cotton causing significant yield losses in the world including Pakistan. The ability of pink bollworms to enter in diapauses before the onset of harsh condition increases the survival rate to greater extent and determine to attain the status of major insect-pest. The present investigations were conducted under laboratory conditions set as 26+2 oC, 65+5% and 15:9 (L/D) temperature, relative humidity, photoperiod respectively. Change in temperature to varied extent and episodes of photoperiod for specific intervals were the key variables to study their influence on diapausing ability in pink bollworms. The results elaborated that the temperature of 14 oC found to be optimum for diapause induction as maximum (68.21±1.83%) larvae of pink bollworms at 4th instar were in diapause state. While the temperature of 26 oC found to be lethal regarding diapause induction of 0.00, 3.11±1.03 and 21.96±0.13% when 4th instar larvae were held for one, four and seven days respectively. Influence of photoperiod revealed that the highest diapause (28.01±0.20%) was induced when episode of 07:17 (L/D) photo phase was maintained for a period of seven days. Peak adult emergence (92.13±3.74%) was recorded at 26 oC, 15:9 L/D of temperature and photoperiod respectively. However, maximum adult mortality (31.66±4.59%) was found at 14 oC when the pupae were held for 14 days. These findings lead to the conclusion that the temperature and photoperiod are the key determinants among the abiotic variable, which govern diapausing phenomena in pink bollworm.