Not really a disease, but the result of a surface saprophyte taking up residence on the turfgrass leaf blade. Saprophytes feed only on decaying mater and not living mater such as a leaf blade. The slime mold actually lives on the decaying matter in and on the soil. Sometimes, they use the grass blade to support their reproductive structures. When these reproductive structures become too massive, some damage may to the grass blade may happen in some instances.
The slime mold fungi initially is seen as a creamy white to greasy black, slimy growth. In time this growth will change to an ashy to bluish gray appearance that is somewhat powdery to the touch.
There is no chemical control of the slime molds. Time is the best cure. They can also be removed through the blast of a garden hose, mowing, brushing or raking will reduce the slime mold populations.