Parasitism and Suitability of Trichogramma chilonis on Large Eggs of Two Factitious Hosts: Samia cynthia ricini and Antheraea pernyi.

Simple Summary: In China, the large eggs of the Chinese oak silkworm (COS), Antheraea pernyi, have been extensively utilized as beneficial factitious hosts for the mass rearing of parasitoid wasps and in the biological control of agricultural and forestry pests. Furthermore, the eri silkworm (ES), Samia cynthia ricini, has a widely distributed large egg that has the potential for use in the mass rearing of Trichogramma parasitoids. This study investigates the role of T. chilonis as a dominant Trichogramma species in lepidopteran pest control for agricultural and forestry production. It offers a comparative analysis of T. chilonis parasitism and suitability with respect to the large eggs from two factitious hosts, the ES and COS. The results reveal the feasibility of mass producing T. chilonis using ES eggs and provide insights into this species' parasitism of both COS and ES eggs. These findings are crucial for developing a cost-effective strategy for large-scale Trichogramma rearing using ES eggs, contributing to efficient biological pest control in agricultural and forestry contexts. Trichogramma, an effective biological control agent, demonstrates promise in environmentally sustainable pest management through its parasitic action toward insect eggs. This study evaluates the parasitism fitness and ability of T. chilonis with regard to two factitious host eggs, aiming to develop a cost-effective biological control program. While T. chilonis demonstrated the ability to parasitize both host eggs, the results indicate a preference for ES eggs over COS eggs. The parasitism and emergence rates of T. chilonis regarding ES eggs (parasitism: 89.3%; emergence: 82.6%) surpassed those for COS eggs (parasitism: 74.7%; emergence: 68.8%), with a notable increase in the number of emergence holes observed in the ES eggs compared to the COS eggs. Moreover, the developmental time of T. chilonis for ES eggs (10.8 days) was shorter than that for COS eggs (12.5 days), resulting in a lower number of dead wasps produced. Notably, no significant difference was observed in the female ratios between the two species. A comprehensive analysis was conducted, comparing the size and shell thickness of the two factitious hosts. The ES eggs exhibited smaller dimensions (length: 1721.5 μm; width: 1178.9 μm) in comparison to the COS eggs (length: 2908.8 μm; width: 2574.4 μm), with the ES eggshells being thinner (33.8 μm) compared to the COS eggshells (47.3 μm). The different host species had an effect on the body length of the reared parasitoids, with T. chilonis reared on COS hosts exhibiting a larger body length (female: 626.9 µm; male: 556.7 µm) than those reared on ES hosts (female: 578.8 µm; male: 438.4 µm). Conclusively, the results indicate that ES eggs present a viable alternative to COS eggs for the mass production of Trichogramma species in biological control programs. [ABSTRACT FROM AUTHOR]