Pythium Blight

This disease is caused by a fungus that can spread quickly to destroy large lawn areas. Cool-season grasses such as tall fescue and ryegrasses are more susceptible to attack than warm-season grasses. Pythium blight is favored by hot (80 to 95 degrees F), humid weather and excessive fertilizer applications of nitrogen. Infected leaves look water-soaked, copper-colored, dark brown or black in color, and feel greasy. Fungal strands may be visible during the evening or early morning hours. Pythium blight can be spread by lawn equipment, foot traffic, and surface water.

Control: Do not mow when the fungal strands are present to avoid spreading this disease. Follow a balanced fertilization program. Remove any thatch layer if it exceeds one-half inch in depth. Water early in the morning to allow the leaves to dry before nightfall. When you irrigate, water deeply and infrequently. Increase air circulation, if possible, by selectively pruning shrubs and trees. Fungicides are available.