Effect of individual quick freezing treatment and cold storage on the host egg (Lepidoptera: Saturniidae) quality for the production of the parasitoid Anastatus japonicus Ashmead (Hymenoptera: Eupelmidae)

Abstract

Background The augmentative release of the parasitoid species Anastatus japonicus Ashmead (Hymenoptera: Eupelmidae) is essential for managing the recent invasion of litchi stink bugs (Tessaratoma papillosa (Drury)) (Hemiptera: Tessaratomidae) in Taiwan. The mass release program in the spring targets this univoltine pest’s reproduction cycle. Low-temperature storage for the host eggs and parasitoids is required to maximize the production for the annual release program. This study aimed to enhance the shelf life of Samia cynthia (Lepidoptera: Saturniidae) eggs using the combination of refrigeration and individual quick freezing (IQF) as a storage treatment. Storage of A. japonicus in the IQF-treated S. cynthia eggs was evaluated to determine the optimal production process during the short preparation window before the release. Results The influences of cold storage and IQF treatment on the host eggs were evaluated for different storage durations. The host quality was determined according to the emergence rate and female ratio of A. japonicus. The study’s results demonstrated that the host quality of S. cynthia eggs did not change significantly compared to the control group after 28 d of refrigeration at 7 °C. IQF treatment extended S. cyathia’s shelf life to 5 months without significantly affecting the host quality. Applying IQF at different developmental stages of the host eggs affected the parasitism rates of A. japonicus. Significantly higher emergence rates of A. japonicus were recorded in the eggs treated during the initial development (D0 to D2). However, storing parasitoids in the IQF-treated eggs under the current storage condition for one month at 12 °C significantly impacted the parasitoid’s emergence rate. Conclusions The results of this study highlight the potential benefits of the individual quick freezing technique. This technique didn’t alter the egg quality of S. cynthia, a crucial factor for the mass production of A. japonicus. The IQF treatment extends the shelf life of the host eggs to 5 months when stored at − 20 °C, a significant improvement compared to the 4-week shelf life without IQF treatment. This technology offers a promising and efficient approach for the mass production of A. japonicus and supports field releases. The treatment allowed for the stockpiling of host eggs during the off-season, which can help expedite the mass production of A. japonicus to fit an eight-week production window.