Population Genomic Insights into Fall Armyworm IPM

The fall armyworm (Spodoptera frugiperda) is a highly polyphagous agricultural pest native to the western hemisphere. Although primarily a pest on grass crops such as corn and sorghum, this insect is often found opportunistically feeding on cotton, alfalfa, soybean, and barley. In the United States, the fall armyworm only overwinters in South Texas and South Florida. However, due to their propensity for long distance dispersal, these insects are capable of establishing populations as far north as Canada by the fall. Additionally, within the fall armyworm, there are two morphologically identical but genetically distinct host associated strains, commonly referred to as the corn strain and the rice strain. These host strains have a sympatric distribution, but show a slight difference in their host plant preferences and responses to chemical insecticides. The aim of this study was to use population genomics to characterize the spatiotemporal population structure and host strain hybridization patterns of fall armyworms originating at the south Texas overwintering site. To do this, we collected moths from five locations and three time points across their central US migratory route, and used ddRadseq to identify single nucleotide polymorphisms (SNPs). Using the identified SNPs, we gained new insights into the population structure of this species, and identified novel patterns of host strain hybridization. Better understanding of fall armyworm population structure and host strain hybridization patterns in the U.S. could lead to more targeted pest management strategies for this species.