Environmentally damaging invasive plants can also serve as reservoir hosts for agricultural pathogens. Microstegium vimineum is an invasive C4 annual grass that is present throughout the midwestern and eastern United States. It can reach high densities in disturbed areas such as crop-forest interfaces, which creates the potential for pathogen spillover from M. vimineum to agricultural crops and native plants. A previous study that surveyed disease on M. vimineum found a large-spored Bipolaris species that was widespread on M. vimineum and also isolated from co-occurring native grasses. Here, we report that the large-spored fungus isolated from M. vimineum and the native grass Elymus virginicus is Drechslera gigantea, based on comparison with published descriptions of morphological traits, and establish that D. gigantea is a pathogen of M. vimineum and E. virginicus. We review the phylogenetic placement and taxonomic history of D. gigantea and propose that it be reassigned to the genus Bipolaris as Bipolaris gigantea.
Keywords: Elymus; Helminthosporium; 1 new taxon; emerging pathogen; stiltgrass.