Above is a photograph of Creeping Rivergrass with spots on the leaves. The disease causing them is blast, the same disease found in rice. In this instance it actually behaves as a mild herbicide slowing down the growth of the plants. I have seen the disease on many grasses over the years and this one has been confirmed by Dr. Groth who was able to isolate blast spores from the lesions a couple of years ago.
The LSU AgCenter and the LSU College of Agriculture