GardenLine | Yard & Garden | Slime Mold: The Blob on the Lawn

After an extended period of heavy rain an organism known as Slime Mold (Mucilago sp., Physarum sp., Fuligo sp.) may appear in your lawn. Slime mold takes many forms. The most common forms on turf resemble small purple or black ball attacked to a blade of grass or a readily noticeable creamy-white to yellow-orange jelly-like mass situated on the lawn.

Life Cycle and Description

Slime mold must have been the inspiration for many "B" grade monster movies.

Slime mold is a primitive organism that has properties of both an amoeba and a fungus. The slime mold produces spores that are capable of amoeba-like movement. The motile spores feed on fungi, bacteria, other micro-organisms, and decaying organic mater. The slime mold spores consume food by simply engulfing particles as they move. The single cell spores multiply by division. The spores pair off and become a shapeless slimy mass, that may flow to the soil surface. Movement of the slimy mass is encouraged by moist cool conditions. The slimy mass flows on to low-lying but upright objects such a blades of grass and garden walls. Once the slime mold mass is located on an upright object, it produces fruiting bodies that produce new spores.

Damage and Control

Slime mold for the most part is a beneficial organism that decays dead plant material, returning nutrients to the soil. It is not a disease, but turf that has been shaded by slime mold may be more susceptible to turf diseases.

Chemical control is usually not necessary. Raking up, and disposing of the slime mold is usually all that is required. If you choose a chemical control, mancozeb (Dithane) is effective.

The slime mold will go away in warm-dry weather conditions.

Sources:

Compendium of Turfgrass Diseases. Richard W. Smiley Ed. The American Phytopathological Society, 1983.

Turfgrass Management. A.J. Turgeon. Reston Pulishing Co. Inc. 1980

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Sustainable horticultural information, offered free of charge to the public with the support of the University of Saskatchewan Extension Division, the Department of Plant Sciences and the Provincial Government.