A long cold storage protocol for <i>Anisopteromalus calandrae</i> based on promoting prepupal development and arresting early pupal growth under low temperature

Anisopteromalus calandrae (Howard) shows great promise as an ectoparasitoid for controlling various coleopteran pests in warehouses. However, for a large-scale release, it is crucial to establish an ample supply of A. calandrae while carefully maintaining their quality and effectiveness. Appropriate cold storage techniques are the key to achieving these goals. Previous studies on cold storage have focused on specific developmental stages and explored cold storage conditions that can be applied only to those stages. Herein, we examined the development, survival and reproductive capacity of A. calandrae at different temperatures (13, 16, and 19 °C) and storage durations (30, 60, and 90 d) and evaluated the fitness of the offspring. A. calandrae completed its egg-to-larva development and pupated at 16 °C, but its development was arrested at an early pupal stage. Even after 90 d of cold storage at 16 °C, the survival rate of A. calandrae remained high at 77%, with no significant impact on reproductive capacity. Furthermore, cold storage showed no negative effect on the F₁ generation. In contrast, eggs stored at 13 °C failed to hatch, whereas those stored at 19 °C developed. Adults emerged after > 60 d. This indicates that storage at 19 °C is only suitable for short durations. Our findings highlight the developmental pattern of A. calandrae at 16 °C, indicating that the parasitic wasp can be stored for a long time at this temperature across all stages of development before pupation, substantially facilitating its mass reproduction and industrial production.