Effects of photoperiod and temperature on development and diapause induction in the Okayama population of Helicoverpa armigera (Hb.) (Lepidoptera : Noctuidae)

The effects of temperature and photoperiod on the development and diapause induction of Helicoverpa armigera (Hb.) were examined under laboratory cond itions. The larvae reared at 20 degrees C under short as well as long photo periods entered diapause at different rates in the pupal stage, except at 1 7L:7D. The critical photoperiod for diapause induction was between 12L:12D and 13L:11D. Irrespective of photoperiod, the larvae reared at 15 degrees C entered diapause, while those reared at 30 degrees C did not. The developm ental periods for eggs, larvae and pupae (non-diapausing) shortened with in creasing temperature were 5.7 and 2.3, 29.0 and 10.6 days, and 25.9 and 9.2 days at 20 degrees C and 30 degrees C, respectively. The developmental thr eshold temperatures for the egg, larva and pupa were 10.8 degrees C, 13.6 d egrees C and 14.6 degrees C, respectively. Furthermore, the effective tempe rature sums for development were 45.5, 200.0 and 142.9 day-degrees (D degre es), respectively. The heat requirements indicate that the insect may compl ete a maximum of four generations per year in southern Okayama Prefecture, western Japan.