Abstract:

【Objective】The effect of fluctuating thermal regimes (FTRs) and the different hosts on the cold survival of the parasitoid Aphidius gifuensis at mummy stage were studied to find out the best conditions and host for the cold-exposured storage of A. gifuensis. 【Method】The emergence rate, male proportion and metathoracic tibia length of the A. gifuensis were recorded and analyzed after treatments of FTRs (4℃ 22 h/20℃ 2 h,4℃ 46 h/20℃ 2 h,4℃ 70 h/20℃ 2 h) on the different mummies of Myzus persicae and Schizaphis graminum. 【Result】 Compared with the control of constant low temperatue (4℃), the emergence rate of cold-exposured A. gifuensis was improved under the treatments of FTRs . The emergence rate in mummies of M. persicae after 2 weeks of 4℃ 22 h/20℃ 2 h (T1) treatment was the highest (78.33%), while the emergence rate in mummies of S. graminum after 1 week of 4℃ 46 h/20℃ 2 h (T2) treatment was the highest (68.33%). There were no significant effects on the male proportion (0.3-0.5) under different temperature treatments. However, the emergence rate in mummies of M. persicae was significantly higher than that of S. graminum, and there were no significant differences in the male proportions and the metathoracic tibia length.【Conclusion】The emergence rate of A. gifuensis under treatments of FTRs was higher than that of the control (exposed at 4℃), and the male proportion was lower than the female proportion. The 2 weeks of 4℃ 22 h/20℃ 2 h treatment in mummies of M. persicae was the best conditions for the production and release of A. gifuensis.

Key words: Aphidius gifuensis, Myzus persicae, Schizaphis graminum, cold exposures, fluctuating thermal regimes