Bag of Heritage G Fungicide. Probably cost you about $60 for 30lb bag. Rate is like 2lb/1000. Way more than you need for such a small area. Or you could go to Homestore and get something labeled for Large/Brown Patch.( Rizoctonia) Bayer usually has something on the shelf. Will involve mixing in a hand sprayer for the homestore method.
"The Poor Fish" circa 1930's: The Poor Fish wouldn't have been caught if he'd known enough to keep his fool mouth shut.