Brown Patch/Large Patch (fungus - Rhizoctonia solani): Turf grass affected by Brown Patch will generally exhibit a light golden brown circular patch or crescent shape. Within the circular areas the grass may be green and recovering. Patches can start unnoticed and reach to be 50 feet in diameter.
Infections are noticeable by yellow leaves at the edge of patches as the leaf sheaths become rotted. A gentle tug on the leaf blade easily separates from the runner (stolon). The leaves will be dark to black where the leaf was attached to the stem or runner.
Brown Patch commonly develops in the fall when day temperatures are between 75 and 85 oF and night temperatures are below 68 oF along with wet conditions. Avoid late night watering if possible. Wet grass and cool nights encourages the disease to thrive and spread. Early morning watering is best, so that the lawn has time to dry out during the daylight.
Brown Patch will not typically kill the grass but does weaken and makes it unsightly. Brown Patch areas will be the first to go dormant in the winter and last t
o green up in the spring as temperatures warm.
A fungicide treatment will be needed to control the active disease. It is recommended that a fungicide treatment is to be watered lightly to activate the control and then to let the lawn dry out as much as possible. Fertilization will not solve the problem and may make it worse as the pathogen feeds off new flush growth of the turf grass.
There have been studies on Brown Patch prevention. These studies have shown to prevent the disease however the timing must be exact with costly multiple treatments. Therefore, we do not recommend prevention other than proper cultural practices.