BROWN CIRCLETS OF DEAD GRASS: In the winter, our St. Augustine grass shows distinctive circular dead areas several feet in diameter. What is the cause? - Palm Beach County

ANSWER: This appears to be brown patch disease, caused by the fungus Rhizoctonia solani. According to Turfgrass Pathologist Dr. Monica Elliott, this is the easiest turf disease to diagnose, especially in St. Augustinegrass. In the margin of the dying grass, gently pull one of the young leaves.

If the whole leaf or a small bundle of leaves pulls out of the clasping, lower leaf sheath, it's brown patch disease. The distinctive circular "donuts" of dead grass, with greenish, recovering interiors, are an ideal, "textbook" example of brown patch disease.

More often the St. Augustinegrass dies in expanding crescents which may touch one another. This is a disease of cool, wet conditions. Dr. Elliott says that in South Florida, the disease is "totally cultural," that is, it can be prevented by not overwatering. In North Florida, where the disease is more prevalent, it may occur despite proper irrigation, during the wetter winters.