Problem: Slime Mould - Physarum cinereum; Mucilago spongiosa

Description:

Slime moulds are commonly found in turf, ornamental, and garden plantings in the home landscape. Slime moulds are primitive organisms that feed on bacteria, other fungi and dead organic matter. Slime moulds often cause concern to homeowners because their reproductive phase is colorful and quite noticeable on plant parts. On turf, large numbers of small gray, white, or purple fruiting structures, called sporangia, form on the leaf blades during cool, humid weather throughout spring, summer, and fall.
Generally, these fruiting structures, ranging in size from small pinhead-size flecks to lumps several inches in diameter, form in small patches (less than one foot diameter) in the lawn. In these small patches, turfgrass foliage may be dotted with the fine specks of the slime mould, or in some cases completely covered by the fungal mass. During wet weather, the fruiting structures may appear slimy. As the structures dry out in hot weather, they become powdery, and break up easily upon touching.
Although unsightly, the slime moulds do not parasitize living plants. Plant structures, such as leaves and stems, serve only as a means of support for the development of the slime mould fruiting structures. Heavy infestations of slime mould may cause a slight leaf yellowing resulting from partial shading of the photosynthetic area. Nevertheless, slime moulds rarely, if ever, cause permanent damage to plants.

Recommendations:

Chemical control of slime mould is not necessary. Frequent mowing and removal of the fruiting structures from plant parts by raking or watering is generally sufficient to improve the appearance of the plant. Excessive thatch or accumulation of organic matter may increase the incidence of slime mould. Therefore, thatch control may help alleviate this problem.