Problem: Take-all Root Rot of St. Augustinegrass
This disease is caused by a fungus (Gaeumannomyces graminis var. graminis) that infects and rots the roots of St. Augustinegrass. It infects only the roots. As they die, the top dies from lack of water. Although the fungus is most active during the wettest season, the symptoms usually become apparent during dry weather, as drought stresses the grass. In some areas, the grass appears to recover in cooler weather, but the disease usually returns the following year. This fungus infects many turfgrasses and cereal grasses, including northern grasses, on which it causes a disease called take-all patch. Favored by wet conditions and alkaline soil, it causes the most damage when turfgrass is under stress.
Because the disease is usually far advanced before symptoms become apparent, it is difficult to control. No fungicides cure the disease, and there are no resistant grasses. To prevent the disease or slow its spread, keep the grass at least 4 inches high, mowing no more than 1/3 of the blade at a time. Water regularly. Deep, infrequent waterings are better than frequent, shallow ones. Remove excess thatch. Control nematodes, insects, and other diseases to lessen stress.