Telenomus remus (Nixon) is a dominant egg parasitoid of the destructive agricultural pest Spodoptera frugiperda (J. E. Smith), and so is used in augmentative biocontrol programs in several countries. An optimized mass-rearing system is essential to produce biological control products in a timely and cost-effective manner. In this study, the photoperiod, host egg:parasitoid ratio, and exposure time were evaluated to identify the optimal rearing conditions for T. remus on the alternative host Spodoptera litura (Fabricius) eggs. Results showed that increasing photoperiod above 12L:12D remarkably improved parasitoid progeny yield and life table parameters. Overlong photoperiods shortened female longevity, but within acceptable limits. There was a significant negative correlation between parasitism rate and host egg:parasitoid ratio under exposure times of 12 and 36 h, but not 24 h. Percentage of female progeny increased significantly along with increasing the host egg:parasitoid ratio. A significant negative relationship between the number of emerged adults per egg and the host egg:parasitoid ratio was observed at an exposure time of 36 h. It was concluded that T. remus may be mass-reared most efficiently on S. litura eggs using a photoperiod of more than 12L:12D, a 14–20:1 host egg:parasitoid ratio, and an exposure time of 24 h. These findings can be used to produce T. remus more efficiently and at lower costs.
Telenomus remus (Nixon) has shown promising potential as a biological control agent for the major invasive agricultural pest, Spodoptera frugiperda (J. E. Smith). Application of biological control programmes in the field requires an efficient mass‐rearing system to provide sufficient numbers of beneficial insects. The short longevity of parasitoid adults and limited period of availability of host eggs are two factors affecting the mass‐rearing efficiency of T. remus. Using Spodoptera litura (Fabricius) eggs as an alternative host, the effects of cold storage of S. litura eggs and T. remus adults at 5°C, 8°C and 11°C for different time durations on the fitness of the parasitoid were investigated to identify the most suitable storage conditions. Results showed that T. remus can successfully exploit stored S. litura eggs, but the number of parasitized eggs decreased with increased egg storage duration and/or reduced storage temperature. For refrigerated adults, the survival rate declined gradually with longer storage duration, and the females' survival rate was higher than the males' at any treatment. Similarly, parasitism capacity of stored adults declined significantly with prolonged storage. Female adult longevity was significantly shorter than the control for all treatments. However, the offspring emergence rate and percentage of females were barely affected by cold storage. In conclusion, S. litura eggs can be stored at 11°C for up to 9 days and adult T. remus can be stored at 8°C or 11°C for up to 7 days without significant losses. Data obtained from this study will help coordinate different aspects of T. remus production, decreasing costs and improving the biocontrol materials' availability.
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