Brown Patch (Rhizoctonia solani), this disease is favored by hot, humid and cloudy weather. Under conditions favorable to the disease, leaves can be killed in 12 to 24 hours. The disease is generally seen in summer and early autumn, although there are strains of this fungus that cause disease at other times of the year. Round or irregularly shaped patches can appear very quickly on turf that is cut closely, such as golf greens, or on turf that is very wet. At first the patches are purplish green in color, but they soon fade to light brown. If the weather is warm and humid, the fungus continues to invade new grass on the edges of the patch, so that there may be a dark purplish to grayish brown border or ring surrounding the spots. This is usually noticeable only in the early morning while the grass is still moist from dew. Dense stands of well-fertilized turf are generally most susceptible to this disease.