During or just after a warm rain or heavy watering, the spores absorb moisture until their walls crack open and release swarming-type spores. These unite in pairs and eventually produce a shapeless, slimy growth called a plasmodium. The plasmodium works its way to the soil surface or out of the thatch layer and creeps over the grass blades, accounting for the slimy appearance. As the plasmodium dies, it becomes the variously colored mass of powdery fruiting bodies that coat the grass blades. The spores are spread by wind, water, mowing, and other activities on the turf.
Slime molds are more of a curiosity or nuisance than a threat to the turf.
Control measures are usually not necessary, but if desired, they are relatively simple. Slime molds can be removed by vigorous raking, brushing, mowing, or hosing down with a fast stream of water. They probably will reappear after the next warm rain, but can be easily removed. Lowering the thatch layer should reduce the food base, and can be used as a preventative. Mushrooms, puffballs, fairy rings and slime molds are part of nature.