مشخصات پژوهش

In order to biocontrol of lepidopteran pests, egg parasitoid, Trichogramma brassicae Bezdenko is reared in commercial insectariums every year. For having a sufficient number of this parasitoid at the release time, it is desirable to store them at low temperatures. Due to the adverse effects of cold storage on the quality of parasitoids, in this study, the effects of cold storage duration on the some biological parameters (parasitization rate, longevity, fecundity, emergence rate and sex ratio) of T. brassicae were investigated. The parasitoid pupae in Phthorimaea operculella Zeller eggs were stored for 1, 4, 7, 15 and 30 days at 4ºC in a refrigerator, RH= 65 ± 10% and full darkness. A control was kept at standard rearing conditions (26 ± 1°C, 65 ± 5% RH with a photoperiod of 16L: 8D). After the time intervals mentioned above, parasitized eggs were transferred from storage to the incubator and maintained at standard rearing conditions to monitor emergence of adult parasitoids. Ten replicates were tested at each storage period. The data were analyzed with ANOVA using SAS and means were separated at the 5% significance level by using Duncan test. The proportion of emerged adults was decreased significantly with increasing the period of cold storage. In the control, 91.88% of adults emerged, but this parameter decreased to 81.11, 78.21, 53.01, 33.15 and 13.51% after 1, 4, 7, 15 and 30 days of storage, respectively. The adults from stored pupae were able to parasitize as well as the control (48.4%) up to 15 days of storage, but adults from 30 days storage pupae significantly parasitize less (29.33%) eggs. The mean of this parameter in 1, 4, 7 and 15 days after storage were 46.28, 46.26, 41.46 and 33.61%, respectively. The longevity of female in control, 1, 4, 7, 15 and 30 days after storage were 6.29, 6.16, 5.24, 4.96, 5.23 and 4.8 d, respectively. There were no significant differences between treatments. The highest and lowest fecundity (56.45 and 38.69 eggs per life sp