The diseases in this group are commonly referred to as melting out, leaf spot, net-blotch, and crown and root rot. These diseases are caused by the fungi Bipolaris, Drechslera and Exserohilum, but were previously classified as Helminthosporium.
Bipolaris species cause leaf, crown and root diseases of fescue, bentgrass, ryegrass, bermudagrass and zoysiagrass during warm, wet weather in midsummer. The diseases generally start as leaf spots and may progress to crown and root rots. Exserohilum has been reported to cause a leaf spot of St. Augustinegrass and bermudagrass. Centipede is rarely affected adversely by these fungi.
Prevention and Treatment
Avoid high nitrogen fertilization and watering practices that provide long periods of wet or humid conditions. Frequent mowing at proper heights will provide better drying conditions in the turf and help to reduce the leaf spot phases of these diseases. Provide adequate water with infrequent but deep irrigation to help avoid crown and root rot phases. Fungicide may be necessary for control. Your Fairway Lawns technician can determine if a fungicide treatment plan is necessary