Even though Louisiana falls are usually dry, rain eventually comes. After long, extended wet periods, a sinister looking fungus or slime may appear, attacking lawns in the cooler season ahead.
LSU AgCenter horticulturist Dr. Tom Koske says slime molds, which appropriately describe these primitive fungi, cover the turf with a dusty-gray, black mass.
"When you look closely, you see tiny, round balls scattered over the foliage," Koske says, adding, "If you rub this dusty coating, a sooty-like powder will cover your fingers. This sooty-like powder is the reproductive spores of these primitive fungi."
This slime mold is one of the Myxomycetes group composed of five genera and about 100 species.
It normally lives unseen on the soil, where it feeds on thatch and decaying organic matter. The black powder also gets on shoes, dogs and kids, but will wash off.
Slime mold doesn’t feed on living plants, but uses the foliage only for support during its reproduction and dispersal. Any damage to living turf and other plants comes from shade, which may cause the leaf blades to temporarily turn yellow. Slime mold doesn’t cause the damage.
The fungus most often occurs in mild, wet weather in spring and in late fall. It disappears rapidly as soon as the air becomes dry. Control is usually not necessary.
You can break up the masses by mowing, sweeping with a broom or by spraying with a strong stream of water. In prolonged damp weather, avoid hosing off because it may spread to where it washes. You can apply a garden turf fungicide to affected areas if desired.
More information on slime mold and lawn care is available at your local LSU AgCenter office.
The LSU AgCenter and the LSU College of Agriculture