Fescue Sod – Powdery Gray Ash

harmless slime mold

Q: I just noticed a powdery gray ash on my tall fescue sod. Is this possibly slime mold? 

A: It sure is! Slime molds are primitive organisms that grow on the surface of grass. They do not hurt grass beyond some yellowing. They often appear on well-maintained turf after a warm summer rain.

A slime mold is composed of thousands of tiny, usually purple, gray, white, or cream, sack-like fruiting bodies. These form in 4- to 6-inch patches in the turf and may be widely spread or clustered into groups. The slimy growth is called a plasmodium. This dries into a powdery mass of spore-bearing bodies that coat the grass blades. Control measures are usually not necessary; but if desired, slime mold can be removed by mowing, or hosing the spot down with a fast stream of water.

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