Impact of low-temperature storage on the performance of Chouioia cunea (Hymenoptera: Eulophidae)

Cold storage is a technique for synchronising mass production of biocontrol agents with release times. Chouioia cunea Yang is an important pupal endoparasitoid of the fall webworm, Hyphantria cunea (Drury). This study aimed to optimise short-term cold storage conditions for last-instar larvae of C. cunea within pupae of the factitious host Galleria mellonella L. Parasitised pupae were stored at 1, 4, 7, and 10°C for 7, 14, 21, and 28 days under dark conditions. A control group was maintained at 26 ± 1°C. Quality control parameters, including adult emergence, sex ratio, fecundity, and life table parameters, were evaluated post-storage. Pre-emergence mortality increased significantly with decreasing temperature and longer storage durations. At 1 and 4°C, mortality exceeded 50% after 14 and 21 days, respectively. In contrast, mortality remained below 20% for up to 21 days at 7 and 10°C. The sex ratio remained strongly female-biased at 7 and 10°C across all storage periods. Fecundity was the most severely affected parameter, with reductions of up to 89% at 1°C for 14 days (21.47 eggs/female) compared to the control (200.45 eggs/female). Notably, the net reproductive rate at 10 °C for 7 days (186.57 offspring/individual) remained comparable to the control (200.45 offspring/individual), indicating that mild cold stress did not impair reproductive capacity. In conclusion, last-instar larvae of C. cunea can be stored for 7-14 days at 7-10°C within G. mellonella pupae without significant negative effects on fitness. These findings provide a practical foundation for improving mass rearing and augmentative release programmes of C. cunea against H. cunea.