What feature distinguishes Brown patch in terms of visual appearance?

The visual characteristic that sets Brown patch apart is the grayish "smoke ring" that appears around the edges of the affected areas. This distinctive feature is a result of the disease's progression, where the inner part of the patch typically dies off and turns brown, while the outer edges remain green for a time, creating a contrast that resembles a smoke ring. This grayish coloration often signals active fungal growth and the transition in the turf's health as the disease spreads outward.

Understanding this visual cue is crucial for accurate diagnosis and subsequent management of the disease, as it helps turf managers quickly identify the problem and take appropriate action. In comparison, other options describe features more associated with different plant stresses or diseases, not specific to Brown patch, which is why they are not the correct choice.