The Extension office has received  several calls over the past couple of weeks seeking information on brown spots that have suddenly appeared in homeowners lawns. Do I have Brown Patch and what is it? Brown Patch is a very common lawn fungus that does attack tall fescue. Tall Fescue is the base for most lawns in this area. Brown Patch Spots vary in color due to mowing height, grass that is greater than 1 inch in height will appear as circle type patches ranging in size from 6 inches to 6 feet in diameter. In regards to color these patches can be brown, tan, or yellow with a very distinctive brown border. Another feature that will aid in identification, when leaves are wet or humidity is high gray cotton type masses called mycelium can be seen growing on affected leaves. If lawns are cut under 1 inch or less Brown Patch will still have the same diameters but will be brown or orange in color. Due to the small leaf surface area lesions and mycelium will not be present,  but often there will be a dark black or gray ring around the patches which helps in identification. This so-called smoke ring will be evident when the lawn is wet or when humidity is approaching 100%.

Brown Patch is a fungus and thrives in hot, humid weather. Development begins when night time temperatures rise above the 60* F mark, Brown Patch thrives when low and high temperatures are greater than 70* F and 90* F . Lawns must be in a wet state for 10 to 12 hours for fungal development to begin which leads to Brown Patch. Other environmental conditions that aid in development are poor soil drainage, lack of air movement, shade, cloudy conditions, dew, overwatering, and watering in late evening. A good cultural practice is to not water after 7pm. 

Over fertilization also leads to fungal development, please take into consideration that a fungus can not produce chlorophyll and is dependent on a food source.

There are preventive and treatment options available. A homeowner should select a Brown Patch resistant variety when establishing a lawn. In regards to fertilization do not apply more than 1/2 lb of nitrogen per 1,000 square feet when conditions favor  Brown Patch development. Please take advantage of the NCSU

Extension soil testing service testing is essential for determining Nitrogen, Phosphorous, and Potassium amounts. Low amounts of Phosphorus and Potassium make damage from this disease more severe. Avoid prolonged periods of wetness, water based on weather conditions. It's best to water just before sunrise, this knocks the dew off of the grass and increases the drying rate. Proper surface and soil drainage also decrease Brown patch infection, so consider purchasing or renting an aerator. Fungicides are also available and can both prevent and cure Brown Patch. Please keep in mind that curative applications to cool season grasses are often ineffective due a slow growth rate during hot conditions. A preventive fungicide regiment is highly effective application should begin in late spring or early summer when night time temperatures exceed 60*F. For a list of Fungicide formulations and rates please visit:
turffiles.ncsu.edu/disease-in-turf/brown-patch-in-turf