Brow Patch appears as irregular circular patches of brown, tan, or yellow grass, 4 to 12 inches in diameter. These patches of dead and dying grass can enlarge and join. The patch perimeter may have a darker border of wilted grass that can be observed in the early morning. Mycelium may be present in wet conditions. In St. Augustine grass, the patch may be brownish in the interior with a yellow outer border ring.
Susceptible species: All major grass types. Especially prevalent in Bentgrasses, ryegrass, blue grasses, and St. Augustine.
Favorable conditions: High humidity, wet soil that drains poorly, excessive thatch, active between 60°-90°F; very active between 80°-90°F.
Chemical control: Preventative fungicide applications should be made when outbreaks are expected to occur during hot, humid weather with high nighttime temperatures.
Photo Credit: William M. Brown Jr., Bugwood.org