LAUSR

Simple Summary The performance of two egg parasitoids T. dendrolimi and T. ostriniae were compared on Asian corn borer (ACB) Ostrinia furnacalis eggs of different ages under choice and no-choice conditions. Both parasitoid species showed significant preferences in parasitizing ACB eggs of different ages. Younger ACB eggs (0–8-h-old) showed high suitability while eggs older than 8 h were not suitable for T. dendrolimi. The age of ACB eggs did not affect the biological parameters of T. ostriniae. Overall, our results highlighted the T. ostriniae species as the best candidate biocontrol agent for managing ACB populations. Abstract The Asian corn borer (ACB), Ostrinia furnicalis, is a serious corn pest in south-east Asia, causing huge economic losses every year. Trichogramma dendrolimi and Trichogramma ostriniae, two egg parasitoids, have previously been identified as key biological control agents. To determine the age impact of ACB eggs on their effective biocontrol potential, herein we compared the biological parameters (i.e., number of parasitized eggs, emergence, developmental time, and sex ratio) of both parasitoids on ACB eggs of various ages (i.e., 0–4, 4–8, 8–12, 12–16, 16–24, 24–36, and 36–48 h old), respectively. Our results showed that the age of ACB eggs had a significant impact on the parasitization activity of T. dendrolimi in both choice and no-choice conditions. Trichogramma dendrolimi preferred to parasitize 0–8-h-old ACB eggs, and its parasitization dramatically declined on ACB eggs older than 8 h under choice and no-choice conditions. On the other hand, T. ostriniae showed high preference to parasitize all tested ACB egg ages. The age of ACB eggs had no significant impact on the parasitization of T. ostriniae under choice and no-choice conditions. Furthermore, the female progeny of T. dendrolimi decreased as the age of ACB increased, while no differences were found in female progeny of T. ostriniae. Trichogramma ostriniae also developed faster on each ACB egg age group in comparison with T. dendrolimi. Overall, the age of ACB eggs had a significant impact on T. dendrolimi performance, leading us to conclude that T. ostriniae is more effective than T. dendrolimi as a biocontrol agent of the ACB.