Effects of collection and storage methods of <scp> <i>Samia cynthia ricini</i> </scp> egg on the reproduction of <scp> <i>Trichogramma chilonis</i> </scp>

BACKGROUND: The eggs of Samia cynthia ricini are a promising host for mass-rearing Trichogramma chilonis, but the effects of egg collection methods, fertilization status, and cold storage on rearing efficiency remain unclear. We evaluated the combined impacts of egg collection methods (spontaneous oviposition vs. manual dissection) and fertilization status on host egg yield and T. chilonis' rearing performance, and examined the cold storage effectiveness for unparasitized and parasitized S. c. ricini eggs. RESULTS: Fertilization status and collection method interacted significantly to affect the host egg yield and parasitoid progeny. Spontaneously laid unfertilized egg treatment had the highest total eggs per female, T. chilonis emergence rate, total progeny, and reproductive coefficient. Spontaneous oviposition outperformed manual dissection, increasing female ratio and emerged adults per egg. At 2 ± 1 °C, underwater storage of unparasitized eggs yielded significantly more parasitized eggs than conventional storage. Compared to fresh eggs, 10-day storage significantly increased total emerged T. chilonis adults and emerged adults per host egg. However, storage beyond 20 days significantly reduced reproductive performance. For parasitized eggs stored at 10 ± 1 °C for 7-21 days, T. chilonis emergence rate and progeny per host egg did not differ significantly from the non-stored control. However, storage for 21 days significantly inhibited progeny emergence. CONCLUSION: Spontaneously laid unfertilized eggs are the optimal host for rearing T. chilonis. Unparasitized eggs should not undergo underwater cold storage beyond 20 days. Parasitized eggs should not be cold-stored over 21 days. These findings offer valuable insights for optimizing T. chilonis mass production. © 2026 Society of Chemical Industry.