Brown Patch is a lawn fungus that appears in humid conditions and presents with circular patches of brown, dead grass. The circles can range from a few inches to a few feet around. The rings are often surrounded by dark, purplish rings and filmy white tufts may cover blades in the early morning dew. After 2-3 weeks, the center brown grass may recover, created a doughnut look. There are several options to control brownpatch, including multiple applications of daconil.