Effect of cold storage temperature on quality of the parasitoid, Trichogrammatoidea bactrae Nagaraja (Hymenoptera: Trichogrammatidae)

This study was designed to find out the optimum cold storage temperature (4, 7, and 10 °C) and storage period (1–16 weeks) of 3 different immature developmental stages (2, 4, 6 days post parasitism) of the egg parasitoid, Trichogrammatoidea bactrae Nagaraja (Hymenoptera: Trichogrammatidae) to produce high-quality individuals to be utilized. Also, the effects of cold storage on parasitoids’ fitness in terms of parasitism percentage, developmental period, adults’ emergence percentage, female percentage, and longevity (fed and un-fed) of parents and F1 progeny were investigated. The obtained results revealed that T. bactrae larvae (2-day post parasitism) could be stored for at least 7 weeks at 10 °C, with least changes in their fitness in both the parents and F1 progeny, followed by 7 °C, whereas storage at 4 °C was the fatal temperature in this early stage of parasitoid with a maximum mortality rate that extended to the next generation (F1). Furthermore, female biased sex ratios were observed at all storage temperatures in the parental and F1 generations but with different values. After a cold exposure of pre- and pupal stages (4, 6 days post parasitism) of the parasitoid at 7 °C, adults’ emergence percentage in the parents was low, but the biological performance in progeny was great. In addition, these late stages could be stored for a short period up to 4 weeks at 10 °C with highest performances in both generations, followed by 7 °C. Ten degrees Celsius proved to be the most suitable storage temperature at different parasitoid ages (larvae, pre-pupae, and pupae). Only the larval stage could continue up to 16 weeks of cold storage, and hence, it can be recommended for a short- and/or a long-term storage period.