Brown patch is a turfgrass common disease that is caused by the Rhizoctonia species fungus. Brown patch can be found in all of the cool season turfgrasses found in the United States. Brown patch is most devastating to: Bentgrass , ryegrass, Annual bluegrass, and Tall fescue. Brown patch is also found in Kentucky bluegrass and Fine fescue but this is rare or does minimal damage. Brown patch is known as a foliar disease, so it does not have any effect on the crown or roots of the turf plant.