One pound of nitrogen per 1,000 square feet should be sufficient. Keep mower blades sharp to reduce the area of open wounds through which fungi can enter. Reduce excess thatch accumulation by aerating annually either in spring or fall. Thatch is a layer of slowly decomposing grass stems, dead roots and debris that accumulates above the soil line and below the grass blades. When this layer reaches more than one-half inch, however, it can cause turfgrass stress.
Turf roots begin to grow in the thatch rather than in the soil.
A thick thatch layer also can enhance the build-up of diseases and an increase in insects. This encourages deep root growth. If powdery mildew and shade are a problem, overseed with varieties of shade-tolerant grass. When controlling any type of disease, insect or weed problems, find out what you can do to discourage pests. Use pesticides only as a last resort and even then only in conjunction with proper turf management.