Brown patch
Rhizoctonia solani
A hot-weather foliar disease producing roughly circular brown patches, often with a smoke ring.
Identification
Circular to irregular patches from a few centimeters to several meters. On close-cut turf a grayish "smoke ring" of wilted, water-soaked leaves may appear at the margin in the morning.
Symptoms
Brown patch symptoms on cool-season turfgrasses are characterized by irregular to circular patches of brown or tan discoloration on the turf. These patches may range in size from a few inches to several feet in diameter. The outer edges of the patch may have a darker "smoke ring" appearance, which is caused by mycelium of the fungus. In addition to the discolored patches, oblong, irregular shaped lesions may also appear on the leaf blades.
Signs
The signs of brown patch on cool season turfgrasses include the presence of profuse mycelium within the "smoke ring" or outer edge of the patch. This mycelium is characterized by its right angle branching and slight constriction at branching points. No spores are present, which can help to differentiate it from other diseases. The mycelium can often be seen growing on the surface of the affected leaves and blades.
Biology
Rhizoctonia solani, the pathogen that causes brown patch, is a soil-borne fungus that can survive in the thatch layer and soil as mycelium. In favorable environmental conditions, the fungus can rapidly produce symptoms within 24-48 hours after infection. In addition to causing brown patch, Rhizoctonia solani can also cause other diseases such as large patch on various warm-season turfgrass species.
Epidemiology
The epidemiology of brown patch on cool season turfgrasses is characterized by the disease being most active in warm, humid weather conditions. The optimal temperature range for the development of the disease is between 70-90°F (21-32°C), with high humidity and extended periods of leaf wetness also being favorable. The disease is most severe during the summer months, particularly in the late afternoon and evening when dew and humid conditions are present. The disease is most common in shaded areas or in turf that receives limited sunlight, and is more severe in low-cut turf, such as putting greens and fairways.
Favorable Conditions
Warm nights (>15.5°C), daytime temperatures 27–32°C, prolonged leaf wetness and high humidity; excess nitrogen aggravates it.
Cultural Management
Cultural control for brown patch includes avoiding excessive watering, improving drainage, increasing air circulation, removing dew, and avoiding high levels of nitrogen during disease favorable conditions. This helps to create an environment that is less conducive to the growth and spread of the pathogen, and can help to prevent or limit the severity of the disease. Additionally, proper mowing and fertilization practices, as well as the use of less susceptible turfgrass species, can also be effective in reducing the risk of brown patch outbreaks.
Further Reading
University extension resources — open in a new tab.
Related Reports
No published reports yet for this pest.
Reports will appear here as they are peer-reviewed and published.