A number of homeowners have called the Extension office recently and asked about a gray powdery substance showing up in their lawns. This fungus-like growth is called slime mold. It looks almost like wood ashes have been scattered in spots on the lawn.
Slime mold commonly occurs on all warm-season and cool-season turfgrasses. Fortunately, it rarely damages a lawn. Its sudden appearance on an otherwise pristine lawn, however, can cause homeowners a great deal of concern.
From a distance, the grass will appear to have turned black or gray, or sometimes, pinkish overnight. On closer inspection, grass blades will be covered with thousands of tiny bead-like specks of slime mold.
The most noticeable signs of this disease are patches of the gray or black crust-like fruiting bodies of the slime mold on the grass leaves. The individual fruiting bodies are about the size of the head of a pin and thousands of them are embedded in the crusty residue on the leaf surfaces.
Slime mold on lawns usually occurs after a rainfall or with frequent irrigation. Slime mold that returns daily on lawns often indicates that the lawn is being watered too often.
In some cases, stalked, brightly colored fruiting bodies may form on the leaf surfaces. These fruiting bodies are filled with dark brown to black powdery spores that are later released. The affected turfgrass appears slimy or oily before the fruiting bodies form and become crust-like.
In most cases, only one or just a handful of slimy patches are found scattered across a lawn, and they often appear in the same area of a lawn year after year. Typically, encrusted grass blades are not discolored or damaged by a slime mold.
After a few days, the crust, or fruiting bodies, disintegrates. The slime mold will then usually disappear without a trace.
Mowing or light raking destroys the crusty fruiting bodies of slime molds. Washing the affected patches of turfgrass with a hard stream of water breaks up the slime mold and restores the lawn’s beauty.
Since slime molds may be more common on heavily thatched or poorly drained portions of a lawn, renovation of the affected areas should reduce the incidence of disease. Thatch can be removed by hand-raking or by using a dethatching machine. Aerating machines are available to aerate and loosen hard, packed soils.
Slime mold may appear on mulch, pine straw or wood chips, as well. If so, it can be scooped up with a shovel and disposed of. Changing to another kind of mulch can prevent slime mold by removing its preferred host.
There are no pesticide sprays recommended for slime molds, and no need to control these odd but harmless organisms. Slime molds usually disappear as quickly as they appear.
As a final note, Carroll County Extension holds a pond management workshop on June 7 at 7 p.m. at the Carroll County Ag Center in Carrollton. For more information, contact Carroll County Extension at 770-836-8546.
Randy Drinkard is the ANR Agent for The University of Georgia Troup/Meriwether County Cooperative Extension. The Troup County Extension office is located at 114 Church St. and can be reached at 706-883-1675. Open Monday through Friday, 8 a.m. to 5 p.m.