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Effects of photoperiod and temperature on diapause induction in Microplitis tuberculifer( Hymenoptera: Braconidae) and the cold storage of its diapause pupae
Pages: 1206-1212
Year: Issue:  10
Journal: Acta Entomologica Sinica

Keyword:  Microplitis tuberculiferdiapausediapause inductionphotoperiodtemperaturecold storage;
Abstract: 【Aim】In order to study what factors impact the diapauses of Microplitis tuberculifer,the effect of temperature and photoperiod on diapause induction and storage condition of diapause cocoons of M.tuberculifer were studied in the field during the late summer and in the laboratory. 【Methods】The diapause rates of M. tuberculifer were investigated in the field cages when the parasitized host larvae were released into the cages every 5 days from August 31 to September 25 and in the laboratory under the conditions of five temperatures( 16,18,20,22 and 24℃) and seven photoperiods( 6L∶ 18 D,8L∶ 16 D,10L∶ 14 D,12L∶ 12 D,14L∶ 10 D,16L∶ 8D and 18L∶ 6D). 【Results】The field tests in the central of Hebei Province showed that when the average daily temperature was 24. 4℃ and the average daylength was 12 hours and 51 minutes,only a few of M. tuberculifer pupae( 5. 08%) entered diapause; and when the average daily temperature was below 17. 2℃ and the average daylength was shorter than 11 hours and 36 minutes,almost all of M. tuberculifer pupae( 99. 70%) entered diapause. No diapause was observed when the temperature was >22℃ regardless of the photoperiod. Only a small part of population( 6. 0%- 25. 9%) entered diapause at20℃ under short daylengths of 6L∶ 18 D to 12L∶ 12 D. In contrast,when the larvae were exposed to 16,18 and20℃ combined with a photoperiod of 10L∶ 14 D,the percentages of parasitoids that entered pupal diapause were100%,89. 75% and 29. 58%,respectively. The emergence rate and the parasitic ability showed no significant difference between adults emerged from the diapause cocoons stored at 0℃ for 240 d and 5℃ for 180 d and those from the non-diapause cocoons without cold storage( P > 0. 05). After cold storage at 0℃ for 300 d,the emergence rate of the diapause cocoons could still reach to 79%. 【Conclusion】Temperature and photoperiod,or their interaction,are the most common diapause-inducing stimuli of the parasitoid. The results of this study would be valuable for mass rearing and storage of diapause cocoons of M. tuberculifer.
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