Phenology overshadows seed treatment and cultivar effects on fall armyworm gut microbiome following short-term feeding on rice

Plants mediate host susceptibility or resistance to infesting insects through various documented ways, and possibly via disrupting insect gut microbiota, an area that is underexplored in rice. The fall armyworm (FAW) (<i>Spodoptera frugiperda</i> (J.E. Smith) is a highly invasive herbivore that infests ∼350 host plant species, including rice (<i>Oryza sativa</i> L.). Exploring the impacts of chemical seed treatments on rice against FAW on the composition and attendant detoxification functionalities of the gut microbiota, as well as the subsequent effect on larval development, could inform the development of more effective management strategies. To test this, we characterized the gut microbiota of FAW 4 th instar larvae exposed to rice cultivars with and without chemical seed treatment (CruiserMaxx plus Vibrance package) at vegetative and reproductive stages for 96-hours. Results did not determine any statistically significant effects of chemical treatments and rice cultivars on larval microbiota composition. However, crop phenology (vegetative and reproductive stages) significantly impacted larval microbiota. Bacterial taxa previously implicated in FAW larval detoxification of plant secondary compounds, as well as FAW growth, and development, were uncovered across larvae. Hence, our findings highlight the importance of considering rice phenology and associated traits in developing management strategies against this highly polyphagous pest.