On close-cut, cool-season turfgrasses, the disease will occur as circular or sometimes irregular patches of light brown turf that range in size from a few inches to several feet (a few centimeters to several meters). During warm, humid conditions, a dark, purplish to grayish-black "smoke ring" or border may appear along the edges of the patches. This ring is the result of the grey pathogen mycelium growing out of the infected leaf blades. The ring is most noticeable in the early morning when dew is still on the grass or during periods of high humidity and free moisture. As the turf dries, the ring will disappear. The smoke ring does not always occur, so it should not be relied upon as the sole identifying characteristic. In most cases, the dead, light brown or straw-colored leaves will be replaced by new shoots initiated from the crown, stolons, and rhizomes.
Brown Patch or Rhizoctonia Blight (Rhizoctonia solani)