Leaf blight disease on the invasive grass Microstegium vimineum caused by a Bipolaris sp.
In 2009, a previously undescribed disease was found on the nonnative invasive annual grass Microstegium vimineum (Japanese stiltgrass). Diseased plants exhibited foliar lesions, wilting, and in some cases, death of entire plants. We identified the causal agent as a Bipolaris sp. similar to B. zeicola. We observed spores and associated structures characteristic of Bipolaris spp. growing from leaf lesions on field collected plants. Pure cultures of the fungus were made and spore suspensions were applied to laboratory-reared M. vimineum seedlings in growth chamber and greenhouse experiments. Initial symptoms appeared on seedlings in the growth chamber experiment within 72 h of inoculation, and seedlings exhibited characteristic lesions within 10 days. The fungus was reisolated from lesions, and the internal transcribed spacer (ITS) region was sequenced to confirm its identity. In the greenhouse experiment, inoculated plants displayed characteristic lesions, and relatively greater spore loads increased disease incidence. Disease reduced seed head production by 40% compared to controls. This is the first report of a Bipolaris sp. causing disease on invasive M. vimineum. Following further analysis, including assays with co-occurring native species, this Bipolaris sp. may be considered as a biocontrol agent for invasive M. vimineum.