Effect of cold storage on performance of Trichogramma brassicae (Hymenoptera: Trichogrammatidae) reared on Ephestia kuehniella and Ectomyelois ceratoniae

Trichogrammatid wasps are the most common natural enemies around the world used for biocontrol many important lepidoptran pests. Therefore, the availability of suitable storage methods for these parasitoids is valuable in biological control. In this study, the performance of Trichogramma brassicae reared on two different hosts and in two different cold storage periods was investigated. Wasp pupae formed on Ephestia kuehniella and Ectomyelois ceratoniae eggs, were kept in 10 ᵒC for 30 days and then in 4 ᵒC for 4 and 8 weeks. The effect of the treatment combinations on wasp's emergence rate, sex ratio and the number of female and male parasitoids in parental wasps (F0) and their progeny (F1) were estimated. In addition, adult wasp's shape (wingless and abnormality) and parasitism rate were investigated in parental wasps (F0) and their progeny (F1). The results of this study showed that emergence rate of T. brassicae in F0 was significantly influenced by the interaction between host and cold storage period. The highest and lowest emergence rate were respectively found on E. creatoniae in control and E. kuehniella in 8 weeks cold storage period. Sex ratio and the number of female parasitoids in F0 and F1 were significantly influenced either by host or cold storage period, whereas interactive effect of these factors did not affect significantly sex ratio and the number of females in both generations. Also, wingless and abnormality of wasps in F0 was not significantly influenced by any treatment combination. Parasitism rate of wasps reared on both hosts in F1, significantly decreased by increasing in cold storage duration. Finally, the results indicated that the most of qualitative characteristics of wasps grown on E. ceratoniae, were clearly better than those of wasps grown on E. kuehniella both in F0 and F1