In North America, there are several hundred species of slime molds. In any one location, there can be up to 50 different kinds. Slime molds are present in all soils. They are common on decaying logs, fallen leaves, mulch, lawns with excessive thatch, and on strawberry leaves.
Although typically classified as fungi, slime molds are unique in their development. Slime molds survive winter in soil and thatch layers as spores. During cool, wet weather, spores germinate and produce single-celled amoeba-like spores (swimming spores). These amoeba-like spores feed on microorganisms and organic matter until some unknown factor causes them to aggregate. These aggregations, called plasmodia, move up out of the soil onto the surface of mulch, wood chips, grass blades, and plant stems. Plasmodia usually appear as white, yellow, gray, or purplish-brown, jelly-like masses. As plasmodia dry, they appear crusty and powdery. Later, crusty reproductive structures called sporangia form. Spores produced from these structures are spread by wind, water, equipment, people, or animals. Spore dispersal is aided by the height gained on grass blades or plant stems.
Slime molds are not parasitic, so they do not cause plant disease. However, heavy coverage on grass or plant leaves may cause yellowing. Control is not usually necessary and slime molds will disappear during hot, dry weather. Slime molds may be washed, brushed, or raked from affected areas. Frequent mowing will quickly remove these fungi on rapidly growing grass.
Compendium of Turfgrass Diseases. R.W. Smiley, American Phytopathological Society, l986. 102 pp. (see page 41).
The Audubon Society Field Guide to North American Mushrooms. l98l. Alfred A. Knopf, New York. 926 pp. (see pages 841-844).
Compendium of Strawberry Diseases. J.L. Maas (ed.), American Phytopathological Society, l984. l38 pp. (see page 55).
Chad Behrendt, Crystal Floyd