GRAY LEAF SPOT. Gray Leaf Spot (pathogen: Pyricularia grisea) is a chronic problem on St. Augustinegrass (Stenotaphrum secundatum) lawns in the southeastern United States. The likelihood of gray spot occurring is during the summer months, June through August. This disease is especially severe during periods of high temperatures and humidity along with abundant rainfall. If conditions are dry, the severity of this disease declines. Gray leaf spot is most severe on newly sodded St. Augustinegrass lawns. Scalping and high nitrogen enhance the severity of this disease.
Gray leaf spot starts off as tiny brown leaf and stem lesions that can rapidly increase in size to oblong spots. The spots are tan to gray with purple to brown borders. When the disease is severe the entire lawn may appear scorched.
Cultural practices that help minimize this disease include avoiding excessive leaf wetness, reducing soil compaction, and avoiding excessive nitrogen applications. Also, on newly sodded St. Augustinegrass turf avoid herbicide induced stress.
SOIL TEMPERATURES.
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