Gray Leaf Spot (Piricularia grisea) usually shows up on St. Augustine Lawns during late spring to early summer, especially if there is abundant moisture available. Spring rains and nighttime watering schedules contribute to disease incidence.
Many times cultural practices contribute to the lawn’s susceptibility to disease. Avoid high nitrogen fertilizers, weed and feed fertilizers and frequent, shallow watering. Do not water in the late evening or overnight.
Catching the clippings while the disease is active will slow the spread of the disease, as will cleaning mower blades with alcohol before mowing healthy turf.
Always check fungicide labels for application rates and recommendations. Be sure that the fungus that you are treating is listed on the label, as well as the grass species that you are treating. The active ingredients Chlorothalonil and Propiconazole are both currently listed for control of Gray Leaf Spot on St. Augustine lawns.