St. Augustinegrass mowed too short, resulting in 'scalped' turfgrass - no disease. Plate 3 . Dry 'patches' in St. Augustinegrass - no disease. A disease is an interaction between the plant and a pathogen that disrupts the normal growth and appearance of the plant. While turfgrasses may be affected by diseases all year, individual turf diseases are active for only a few months each year, usually due to weather patterns and the resulting environmental effects.
Most fungi living in lawns are totally harmless.
It is a very small number of fungi that cause plant diseases. It is important to know that when a fungal pathogen is not actively attacking the plant, it has not disappeared from the turfgrass area. There are two common patterns of turfgrass disease symptoms. One is a circular patch of turfgrass, either small or large, that is no longer uniformly green. The second is turf that has 'spots' on the leaves.