Abstract: 【Aim】 The parasitism rate of Aphidius gifuensis on Myzus persicae is quite high. Therefore, it is widely used for A. gifuensis to control M. persicae in tobacco. However, in the process of artificial propagation of A. gifuensis certain environmental factors may have influences on its growth and development. This study aims to make clear of the effects of photoperiod, humidity and temperature on the parasitism of A. gifuensis on M. persicae. 【Methods】 The parasitism rates on M. persicae nymphs and the emergence rates, longevity, sex ratios (proportions of females) and metathoracic tibial lengths of A. gifuensis adults under the conditions of the temperature of 25℃ and the relative humidity of 70% combined with four photoperiods (9L∶15D, 12L∶12D, 14L∶10D and 19L∶5D), under the conditions of the temperature of 25℃ and the photoperiod of 14L∶10D combined with four relative humidity levels (65%, 70%, 75% and 80%), and under the conditions of the relative humidity of 70% and the photoperiod of 14L∶10D combined with four temperatures (10℃, 15℃, 25℃ and 35℃), respectively, were investigated in the laboratory. 【Results】 The results showed that the growth and development of A. gifuensis were negatively affected by too long or too short photophase. Under the temperature of 25℃ and the relative humidity of 70%, the body size of A. gifuensis adults under the photoperiod of 14L∶10D was the largest, with their metathoracic tibial length under this photoperiod the longest (0.439 mm), while their body size under the photoperiod of 12L∶12D was the smallest, with their metathoracic tibial length the shortest (0.345 mm). Under the temperature of 25℃ and the relative humidity of 70%, A. gifuensis adults under the photoperiod of 14L∶10D had the highest parasitism rate and longevity on M. persicae nymphs, which were 42.61% and 42.33 h, respectively. Under the temperature of 25℃ and the photoperiod of 14L∶10D, the parasitism rates of A. gifuensis adults on M. persicae nymphs increased at first and then decreased with the increase of relative humidity. Under the temperature of 25℃ and the photoperiod of 14L∶10D, the parasitism rate of A. gifuensis adults on M. persicae nymphs under the relative humidity of 75% was the highest (54.44%), while that under the relative humidity of 65% was the lowest (only 21.67%), the longevity and metathoracic tibial length of A. gifuensis adults under the relative humidity of 70% were the longest (42.33 h and 0.439 mm, respectively), while their longevity under the relative humidity of 75% was the shortest (only 20.42 h), and their metathoracic tibial length under the relative humidity of 65% was the smallest (only 0.373 mm). Under the relative humidity of 70% and the photoperiod of 14L∶10D, the temperature of 25℃ was more beneficial to the growth and development of A. gifuensis adults than 10℃ or 15℃, and the parasitism rate of A. gifuensis adults on M. persicae nymphs, and the proportion of females and metathoracic tibial length of A. gifuensis adults at 25℃ were 42.61%, 39.04% and 0.439 mm, respectively, higher than those at 10℃ and 15℃. However, the high temperature of 35℃ was not conducive to the parasitic behavior of A. gifuensis adults on M. persicae nymphs: Under this high temperature, no mummy aphid was found, and even the host aphids were all killed. 【Conclusion】 Under the temperature of 25℃ and the relative humidity of 70%, the photoperiod of 14L∶10D is more beneficial to improve the parasitism rate, body size and longevity of A. gifuensis adults. Under the temperature of 25℃ and the photoperiod of 14L∶10D, the humidity of 75% is more beneficial to improve the parasitism rate of A. gifuensis adults, while the humidity of 70% is more beneficial to the increase of their longevity and body size. Under the photoperiod of 14L∶10D and the relative humidity of 70%, the temperature of 25℃ is more conducive to the increase of their parasitism rate, body size and proportion of females, while the low temperature of 10℃ is more beneficial to prolong their longevity. The results of this study provide scientific references for the artificial propagation and rejuvenation of A. gifuensis in field greenhouses or indoor sheds.

Key words: Aphidius gifuensis, photoperiod, humidity, temperature, parasitic ability, longevity