Variation in Pathogenicity and Host Range ofBipolarissp. Causing Leaf Blight Disease on the Invasive GrassMicrostegium vimineum

Microstegium vimineumis a widespread invasive grass that poses significant threats to forests and disturbed areas throughout the United States. Often, the large-scale, rapid spread ofMicrostegiumprohibits management by traditional methods. Control ofMicrostegiummay be possible through the use of a pathogen (referred to here asBipolarisMv) that causes leaf blight onMicrostegium. Members of the fungal genusBipolarisare known pathogens of many plants, including important agronomic crops. However, little is known about the biology and host range ofBipolarisMv. We used a series of growth chamber and light bank experiments to determine the variation inBipolarisMv from different geographic origins and its ability to cause foliar lesions and chlorosis onMicrostegium. We used petri plate and soil infestation assays to determine the effects ofBipolarisMv onMicrostegiumemergence from seed, biomass, and root necrosis. Finally, we tested the host range of these fungi on economically and ecologically important plant species. All isolates increased disease onMicrostegiumfoliage relative to controls, although the effects varied among isolates. Isolates increased root necrosis by 97% in petri plate assays and by 4% in soil infestation trials compared to controls. Infestation of soils withBipolarisMv reduced emergence ofMicrostegiumfrom seed by 31% compared to controls, but did not affect root or stand biomass.BipolarisMv produced lesions on a range of grasses, including corn, sorghum, rye, and wheat, although lesion size varied with isolate. These results indicate thatBipolarisMv may be an effective pathogen onMicrostegium, but its use as a bioherbicide may be impractical because of its effects on a wide range of grasses.