Abstract: The Asian corn borer, Ostrinia furnacalis (Guenée), exhibits a facultative diapause. Its diapause characteristics play a pivotal role not only in allowing its populations to use the most favorable climatic conditions to the greatest extent, but also in regulating its seasonal population dynamics. The objective of this study is to understand the effects of seasonal cues such as photoperiod and temperature on diapause induction in O. furnacalis, which will provide the scientific evidence for forecasting population dynamics. Effects of photoperiod and temperature on larval diapause were examined under 80% relative humidity and combinations of temperatures 20℃, 27℃ and 30℃ with 11 photoperiods in the environmental chambers (HPS-500 and HPG-320H) with four geographic populations, i.e., Nong’an population (NA) of Jilin Province, Hengshui population (HS) of Hebei Province, Huizhou population (HZ) of Guangdong Province, and Haikou population (HK) of Hainan Province. The results indicated that photoperiod played a key role in diapause induction. Short-day caused larval diapause at 20℃, and the photoperiod response under a series of diel patterns showed that it was a typical long-day insect. The critical day-lengths were 14 h 3 min, 13 h 59 min, 13 h 32 min, and 13 h 7 min for NA, HS, HZ, and HK populations, respectively, which were declined from the north towards the south. The day-length of 12 h induced the highest diapause rate. The sensitivity of larvae in response to the photoperiod for induction of diapause declined with the increase of latitude. However, the photoperiod curve showed that it was a shortday and longday insect at 27℃. There were two critical day-lengths for NA, HS, HZ, and HK populations, i.e., 12 h 50 min and 13 h 32 min, 11 h 35 min and 13 h 8 min, 12 h 58 min and 13 h 1 min, and 11 h 50 min and 12 h 26 min, respectively. The highest diapause rate for each population was significantly lower at 27℃ than that at 20℃. The critical day-length would be shortened when the temperate increased from 20 to 27℃. However, the diapause rate was less than 4.3% at 30℃, suggesting that the diapause was almost inhibited completely. These results demonstrated the compensatory effect of temperature on diapause induction by photoperiod in O. furnacalis. In conclusion, O. furnacalis has a temperature-dependent type I photoperiod diapause response in the nature; the critical day-length of the population increases with its geographical location toward the north; and the population diapause response is also characterized as a short day-long day insect, which may play a key role in the presence of multi-populations with diverse ecotypes of voltinism in one geographic location.

Key words: Ostrinia furnacalis, geographical population, diapause, photoperiod, temperature, diapause induction