Effects of environmental conditions on diapause in native populations of pink bollworm (Lepidoptera: Gelechiidae)

Factors affecting induction and termination of diapause in pink bollworm, Pectinophora gossypiella (Saunders), were studied in several trials with field-collected animals under simulated field conditions from 1983 to 1994. Percentage diapause on 1 Oct had a significant correlation of 0.883 with chill units during the 2-wk period 8-21 Sept. In controlled environments, induction of diapause was delayed by higher temperature (32 degrees C) combined with longer photoperiod (14:10 LD) and accelerated by cooler temperatures (30/15 degrees C) combined with shorter photoperiod (10:14 LD) Additionally, larvae exposed to the modified and controlled environmental regimes for a longer period of time experienced a greater effect. One-, two-, or three-day exposure to the high temperature and longer days had no effect on larval survival 20 days after the beginning of exposure for diapausing larvae cultured at the lower temperatures and shorter days for almost four months and returned to the original culture conditions after exposure. However, exposure for 14 d at the high temperature and long days caused a marked reduction in percentage of larvae remaining in diapause. Results for 5-d exposure at the warm temperature and long photoperiod were intermediate, Moisture, combined with increased temperature and day length, caused earlier release from diapause than increased temperature and day length alone.