Assessing parasitism and suitability of three Trichogramma parasitoids Tuta (=Phthorimaea) absoluta (Meyrick) based on parasitoid and host ages

As a major invasive pest, Tuta (=Phthorimaea) absoluta (Lepidoptera: Gelechiidae) poses a substantial threat to tomato production. The use of egg parasitoids from the family Trichogrammatidae (Hymenoptera) has been identified as a potential biological option for controlling T. absoluta. Furthermore, these parasitoids demonstrate effectiveness in parasitizing and managing pests in outdoor settings. Thus, understanding the effects of parasitoid species and host age on Trichogramma parasitism of T. absoluta is crucial for ecological management in the region. This study aimed to assess the parasitism rates, emergence rates, and developmental dynamics of Trichogramma ostriniae, Trichogramma chilonis, and Trichogramma dendrolimi on T. absoluta eggs of different ages, as well as the parasitism ability of the three Trichogramma species at different ages, to determine their potential for controlling T. absoluta. The results demonstrated that both T. ostriniae and T. chilonis effectively parasitized T. absoluta eggs at all ages. However, as the age of T. absoluta eggs increased, there was a notable decrease in parasitic activity and emergence rates for all three Trichogramma species. Conversely, a proportional increase in total developmental duration was observed with the advancing age of T. absoluta eggs. Notably, when egg age reached 60 h, T. ostriniae and T. chilonis exhibited significantly higher emergence rates of 66.33% and 59.67%, respectively, compared to T. dendrolimi at 46.00%. Furthermore, the adult stage duration and female proportion of the three Trichogramma species remained unaffected by the age of T. absoluta eggs, with T. ostriniae showing superior performance to the other two Trichogramma species. Overall, these findings suggest that T. ostriniae demonstrates broad selective parasitism and host suitability for T. absoluta eggs, potentially positioning it as a dominant parasitoid for T. absoluta control in China.