Growth and reproduction in Heliothis armigera is known to be controlled by temperature, relative humidity and host plants. Photoperiod was also found to be an important extrinsic factor regulating the different biological aspects of H. armigera. The effect of five alternating light and dark cycles on the adult as well as on the immature stages of this pest was studied at 25 ± 2°C.
The results obtained showed that the photoperiod regimes tested on the adult stage has a high significant effect on reproduction and longevity. Also 16 hr photoperiod was the most suitable condition for maximum egg deposition and maximum percentage of egg hatching.
The immature photoperiod regimes had a high significant effect on the larval duration, pupal weight and percentage of emergence of adults, but had no effect on the pupal duration. Combined effect of immature and adult photoperiod regimes affected greatly the fecundity and longevity of the adults.