Molecular quantification of parasitism reveals the competitive superiority of Telenomus remus over Trichogramma parasitoids on fall armyworm

BACKGROUND: Effectively harnessing the biocontrol potential of parasitic wasps requires a precise understanding of their interspecific competition and parasitic efficacy. RESULTS: Using the three dominant egg parasitoids of the fall armyworm (FAW; Spodoptera frugiperda)-Trichogramma dendrolimi, Trichogramma chilonis and Telenomus remus (Te. remus)-as a model system, we first analyzed the parasitic competitive relationships, developed an ITS2-based molecular assay for species-specific identification, and then applied this method to analyze the parasitoids' competitive interactions and quantify their parasitic potential. Competition assays demonstrated that Te. remus achieved superior parasitism performance and produced more progeny with its higher female ratio. Furthermore, we established exponential regression models, which accurately correlated ITS2 gene expression levels with parasitism rates, enabling a direct molecular assessment of parasitic activity. Using these models, we quantified the parasitism rates on FAW eggs as 70.25% for Te. remus, significantly higher than the 41.54% for T. dendrolimi and 36.45% for T. chilonis. CONCLUSION: This research not only provided clear evidence prioritizing Te. remus as a highly effective agent for FAW biocontrol, but also developed a molecular approach for rapid and accuracy parasitoid efficacy assessment contributing to sustainable pest management.