Black Fungus? In the lawn

Asked July 31, 2018, 6:09 PM EDT

We have a dry, non irrigated lawn in Grand Ledge. When my husband mows the front of the tractor and mowing deck turn black. It blows off easily with the leaf blower when he’s done. Just wondering what we’re dealing with, is it harmful to the lawn or people?

Eaton County Michigan lawns

1 Response

Good morning,
Without seeing pictures of the black substance I am only guessing what the problem is. If you have a local Extension Office I would recommend taking sample to be diagnosed. I am sending some information on Slime Mold which I hope will give you an answer on what this black substance is.

Slime mold can affect all turfgrasses but is not considered a destructive disease. Slime mold is a primitive organism (prokaryote) that uses the grass blade for support as it feeds on bacteria, fungi and organic matter such as thatch. The spores typically spread from thatch to the leaf during heavy rain. Although the black and white reproductive structures, called sporangia, often form an unsightly mass on grass leaves in patches as large as 1 foot in diameter, they do not harm the host turfgrass unless the entire blade is covered and its ability to photosynthesize is reduced; such conditions can cause leaf yellowing.

Noticeable masses appear in cool, humid weather and break apart when hot, dry weather returns. Mechanical removal of the fruiting structures can be achieved with a rake, broom or strong stream of water from a garden hose. Chemical control is not warranted.

Chemical control options: Not necessary, but Fore (mancozeb) will provide effective control if coverage is heavy enough to block sunlight from leaves.

Cultural methods to prevent slime mold: Prevent thatch accumulation from exceeding 1/2 inch.

Thank you for using Ask an Expert and Good Luck!