Slime mold (Physarum cinereum) has a similar appearance to that of greasy spot and affects all turfgrasses. The mold patches start out a light grey or white, but as spores grow on the grass blades they turn from gray to black. Unlike greasy spot, however, grass coated in slime mold only looks like it is dying. If you wash the mold from the grass before it is damaged from lack of sunlight, the grass will survive.