A lawn is often a homeowner's largest face to the world, a representation of his commitment to keeping the community and his home beautiful. Diseases on a lawn can be a frustrating problem because they can often be difficult to diagnose and fix. Brown patch grass disease is a common disease in many types of lawn grass. It is caused by a specific set of conditions and can be treated fairly easily using a good watering technique.
Brown patch grass disease is characterized by circular patches of grass that has turned brown. When observed up close, unmowed grass blades will have brown leaf tips and damage on the bodies of the leaves. According to "The Lawn Bible" by David R. Mellor, when mowed, grass affected by brown patch grass disease may exhibit a bluish-colored ring around the perimeter of the affected area.
The brown patches are caused by a lawn disease called rhizoctonia blight. According to the North Dakota State University guide, "Lawn Diseases," brown patch grass disease is caused by a fungus called Rhizoctonia solani. Factors that may contribute to a rhizoctonia infection include dull lawnmower blades, too-frequent watering and temperatures that stay above 65 degrees Fahrenheit in the evening.
Methods to prevent brown patch grass disease caused by Rhizoctonia solani fungus include watering the grass early in the morning and waiting until the grass is dry before watering again, and avoiding night watering. If the brown patches are accumulating in an area under trees or shrubbery, trimming the foliage back may help increase sunlight and the flow of air in the area, which may help to more quickly dry the grass before evening.
Types of grass that are most vulnerable to experiencing brown patches under the appropriate conditions include ryegrass and St. Augustine grass, but brown patch grass disease can affect all types of lawn grass.
Dollar spot grass disease is similar in appearance to brown patch grass disease from afar, but the brown patches are smaller in size--usually less than 6 inches in diameter--and white fuzzy fungus is usually present on the grass. According to "The Lawn Bible," dollar spot grass disease is often caused by wet grass and a nitrogen deficiency, and is most common on Kentucky bluegrass.