Effect of Cotesia ruficrus Parasitization on Diversity and Community Composition of Intestinal Bacteria in Spodoptera frugiperda

Parasitoids have the potential to alter the gut microbiota of their host insects post-parasitization, thereby influencing the host’s physiological functions and creating a more favorable environment for the survival of the parasitoid’s progeny. Cotesia ruficrus is a native enemy of the important invasive fall armyworm (FAW) pest, Spodoptera frugiperda, in China, exhibiting significant pest control capabilities. To investigate the impact of C. ruficrus on the gut bacteria of FAW caterpillars following parasitism, we used 16S rRNA sequencing technology to analyze the diversity and richness of gut bacteria in both long-term laboratory and short-term laboratory FAW caterpillars. The results revealed Enterococcus as the predominant bacteria across all treatments, while no significant differences were observed in the diversity and richness of gut bacteria between non-parasitized and parasitized long-term laboratory FAW caterpillars. Similarly, while the diversity of gut bacteria in non-parasitized and parasitized short-term laboratory FAWs showed no significant variance, a marked discrepancy in richness was noted. Moreover, the richness of gut bacteria in short-term laboratory FAW caterpillars surpassed that of their long-term laboratory counterparts. In addition, it was found that Corynebacterium existed only in the intestinal tract of FAW caterpillars that were parasitized by C. ruficrus. These results substantiate that C. ruficrus parasitization can alter the gut microbiota of FAW caterpillars, providing valuable insights into the interplay between gut microbiota and the dynamics of parasitoid–host interactions.