Survival and life history of Psix saccharicola (Hymenoptera: Scelionidae) in frozen host eggs and after cold storage as pupae

Psix saccharicola Mani (Hymenoptera: Scelionidae) is a key parasitoid of stink bugs eggs in Iranian pistachio orchards, especially Acrosternum arabicum Wagner (Hemiptera: Pentatomidae). Cold storage of host and parasitoid life stages can facilitate parasitoid production and assist application timing in augmentation programs. We tested the suitability of A. arabicum eggs stored at –20 °C and –80 °C for periods of 0 to 90 d for parasitism by P. saccharicola. The fecundity of F1 females declined with duration of host egg storage, more so at –80 °C than at –20 °C, and so did immature survival and sex ratio. Duration of egg storage, but not temperature, affected the survival of F2 parasitoids. The 24-h fecundity of F2 females, their progeny survival and sex ratio, did not differ from controls even when parental host eggs were stored for 60 d at –20 °C, but the sex ratio was reduced by storage for 15 d at –80 °C. Parasitoid storage as pupae at either 6 °C or 8 °C for 0 to 28 d (with 2 h daily at 27 °C) had no effect on 24-h fecundity, percent parasitism, or sex ratio, but survival declined with storage time, falling to ca. 30% and 50% after 28 d at 6 °C and 8 °C, respectively. Progeny sex ratio of the F2 generation declined progressively with storage duration at 6 °C, but not at 8 °C, whereas other fitness measures were unaffected. We conclude that the use of frozen host eggs and refrigerated pupae could facilitate the rearing and augmentation of P. saccharicola against stink bug pests of pistachio.