Karl Forester diseases
I planted my new 1 gal Karl Forester grasses in Grand Marais about 1 month ago. The soil is mainly sandy and I have been watering regularly. Now on the blades are black little lines and some of the blades have turned golden color. I looked at a picture of miscantus with a fungal disease and it looks very similar. Will the grasses recover and what should I do next? They are planted in mostly sun and are spaced about 18" - 20" apart.
It sounds like your plant may have foliar rust disease. It is a fungus that occurs in late summer/early fall during years when rainfall has been high. No treatment is necessary at his time of year. I would suggest continuing to water, if necessary. In late fall cut the grass down and dispose of rather than compost. Chances are the grass will establish with healthy new shoots next year.