Gray Leaf Spot Outbreak

Gray leaf spot is rampant in Texas currently. This photo from a reader is one of the worst examples I’ve ever seen. Viewed from afar, the affected turf shows irregular sweeps/washes of light green/yellowing grass among normal areas. Closer inspection of the blades shows the lesions, but rarely this bad. They’ll most commonly be along the midribs of the blades and even on the runners. They’ll usually be rounded or diamond-shaped, brown with gray centers. This is a summer disease, and it almost always follows applications of nitrogen – nitrogen fertilizer can send it out of control. And our first response to yellowing grass is often to apply more nitrogen, and the cycle spins worse and worse. Controls: applying a turf fungicide will help somewhat, but the best remedy is to avoid fertilizers entirely in June, July and August. We tend to over-feed St. Augustine anyway.