Diapause termination in Sesamia nonagrioides (Lepidoptera: Noctuidae) under laboratory and field conditions

The influence of photoperiod and temperature on the termination of diapause of Sesamia nonagrioides (Levebvre) was evaluated under laboratory and field conditions. Long-da,: photoperiod enhanced termination of diapause. Larvae held under a short-day photoperiod (10:14 [L:D] h) for various times and then transferred to a long-day photoperiod (16:8 [L:D] h) proceeded to pupate in approximate to 14 d, indicating that regardless of the state of diapause intensity, diapause completion and postdiapause development listed similar lengths of time. Larval diapause termination was not hastened when diapausing larvae kept at a photoperiod of 10:14 (L:D) h and 25 degrees C were exposed for short periods at 30, 35, and 40 degrees C. whereas it was shortened when diapausing larvae were transferred from 25 to 30 degrees C and kept continuously at this temperature. At higher temperatures (35 and 40 degrees C), all transferred larvae died. It was also shown that exposure of diapausing larvae to low temperature (5 degrees C) simply accelerated diapause development but termination of diapause did not require a period of chilling. Moreover, after low temperature treatment. diapausing larvae showed a faster diapause development when transferred to a long-day photoperiod than those kept in a short-day photoperiod. In thr latter case, the longer the exposure the faster the termination occurred. Diapause termination of field-collected larvae was practically spontaneous. After transfer to laboratory conditions, 25 degrees C and a photoperiod of 16:8 (L:D) h. they quickly proceeded to pupate. Field-diapausing larvae terminated diapause in January but exhibited. a postdiapause development; the Ist record of pupation was observed in the field at the end of March.