Dollar spot forms hour-glass shaped lesions with reddish brown margins on Kentucky bluegrass and tall fescue. The lesions are often near the tip of the leaf on perennial ryegrass and creeping bentgrass, so the hour-glass is not as apparent. Pythium and brown patch are most often seen on annual bluegrass, perennial ryegrass, and creeping bentgrass in higher N areas, drainage swales, and other wet or humid areas. Pythium mycelium is a pink to gray and grows out of living tissue. Brown patch mycelium is not as common, but it is a grayish-brown color sunken down below the turf canopy.
Brown patch forms very irregularly shaped legions, with reddish brown margins.
If you are unsure which disease you see, contact the Purdue Plant Pest and Diagnostic Lab . The information given herein is supplied with the understanding that no discrimination is intended and no endorsement by the Purdue University Cooperative Extension Service is implied. Any person using products listed assumes full responsibility for their use in accordance with current direction of the manufacturer. Information listed is valid only for the state of Indiana.