Abstract:  To understand the geographic adaptation and geographic variation of diapause intensity in different geographic populations of the cotton bollworm, Helicoverpa armigera, the effects of photoperiod and temperature (daylengths of 11-16 h, constant temperatures of 20, 22, 25, 28 and 31℃, and thermoperiod) on diapause intensity of H. armigera from 4 different geographic populations (Guangzhou population, Yongxiu population, Tai’an population, and Kazuo population) were investigated. The results indicated that the photoperiods for diapause induction ranged from 11 to 14 h, and the daylength had a significant influence on diapause intensity. The duration of diapause in the four different geographic populations gradually prolonged with the daylength increasing. The diapause intensity was also affected by the thermoperiod for diapause induction. When the photophase temperature was the same, Guangzhuo population from low latitude showed longer diapause duration at thermoperiod than at constant temperature; there were no significant differences in the duration of diapause between the thermoperiod and constant temperature in Yongxiu population from mid-latitude; on the contrary, the diapause duration induced at thermoperiod temperature was shorter than that at constant temperature in northern Kazuo and Tai’an populations. Temperature during diapause significantly affected diapause duration, at 20-31℃, and the duration of diapause was significantly shortened with the temperature increasing. However, the duration of diapause was also affected by the temperature for diapause induction. Higher constant temperature induced a stronger diapause in northern Kazuo and Tai’an populations.

Key words: Helicoverpa armigera, diapause intensity, diapause duration, thermoperiod, photoperiod, geographic variation