Cold storage of Gonipterus platensis (Coleoptera: Curculionidae) eggs for Anaphes nitens (Hymenoptera: Mymaridae) rearing

Abstract

BACKGROUND : Anaphes nitens (Girault, 1928) (Hymenoptera: Mymaridae) is an egg parasitoid used for the biological control of Gonipterus spp. in regions where this pest is present. Cold storage of host eggs is a crucial strategy in biological control programs. This study aimed to evaluate the effects of cold storage on G. platensis eggs for laboratory rearing of both the host and its parasitoid, A. nitens. METHODS : Gonipterus platensis eggs, aged 1 and 3 days, were stored in a refrigerator at 7 ± 1 °C for 5, 10, 20, 30, 40, and 50 days in complete darkness. After each storage period, the eggs were transferred to a biochemical oxygen demand (BOD) chamber at 25 °C and hatching rates and larval survival were assessed. To evaluate parasitoid reproduction, fresh host eggs were stored at 7 ± 1 °C for 5, 10, 15, 20, and 25 days under dark conditions and subsequently exposed to A. nitens. Parasitism rate, sex ratio, and offspring longevity were recorded. RESULTS : Results showed that 1- and 3-day-old G. platensis eggs maintained the highest viability within the first 10 days of storage, with hatching rates exceeding 50% up to 20 days post-storage. A 20-day storage period was the longest duration that did not differ significantly from the non-stored eggs (control) considering A. nitens parasitism and progeny longevity when stored host eggs were offered. CONCLUSION : Therefore, storing host eggs for this period effectively supports colony maintenance while simultaneously facilitating parasitoid propagation.