Research on the induction and termination of diapause in Trichogramma dendrolimi
Author of the article:ZHOU Shu-Xiang , LU Xin**, ZHANG Guo-Hong , LI Li-Juan, DING Yan
Author's Workplace：Institute of Plant Protection, Jilin Academy of Agricultural Sciences, Gongzhuling 136100, China
Key Words： Trichogramma dendrolimi, diapause induction, diapause termination
Abstract： [Objectives] To determine the optimum conditions for the induction and termination of diapause in Trichogramma dendrolimi in Antheraea pernyi eggs. [Methods] The effects of age (parasitoids developed for 40、96 and 144 h after parasitization at 26℃), temperature (10, 13 and 16℃), and low temperature exposure period on diapause rate were investigated to determine the optimum conditions of diapause indication. The emergence rate, emergence synchronism and number of wasps emerged per Antheraea pernyi egg post diapause termination after cold storage at different temperatures for different periods were investigated to determine the conditions required for the termination of diapause. The effects of diapause inducing temperatures on diapause termination were also studied. [Results] Diapause was induced in insects of different ages by exposure to constant low temperatures , but the highest diapause rates (100% and 99.12%, respectively) were achieved when young larvae (26℃ for 40 h) were exposed to 31 days of low temperature at 10 and 13℃. Diapause termination of T. dendrolimi, and its post-diapause emergence was affected by both diapause induction temperature and cold storage temperature. Diapausing prepupae that were inducted at 10℃ and then stored at 1℃ had a shorter diapause breaking time, a higher emergence rate, and a longer storage period. These pupae stared to emerge normally, when transferred to 26℃ after being stored at 1℃ for 30d. After being stored for 60 d, the emergence rate reached 95.24% and the emergence rate was higher than 60%. More than 50 wasps emerged per host egg after storage for 4 months. [Conclusion] The optimum conditions to induce diapause in T. dendrolimi consisted of keeping the parasitoids at 26℃ for 40 h, and then moving them into 10℃ for 31d; the optimum diapause breaking conditions were storing diapausing prepupae at 1℃, however the storage period should be not exceed 4 months.