Slime Mould

Slime moulds occasionally appear on lawns in moist and warm conditions. Slime moulds are primitive fungi that vary greatly in colour, size and form but are often seen as a slimy, creamy-white, yellow or black substance on lawns. Slime moulds use living grass plants for structural support; they do not attack or kill the grass. The moulds may appear and disappear quite suddenly, most typically in late summer and autumn. 

Slime moulds are primitive organisms, once considered to be fungi but now recognised as single-celled organisms similar to amoeba. Slime moulds do not attack plants, they feed on the bacteria of dead and decaying matter and use the grass to support themselves when grouping together to form spore producing structures. 

No control is required, slime moulds do not harm the grass and will quickly disappear. If the appearance is particularly bothersome, slime mould can be removed using the spray from a garden hose but the best course of action is to leave the mould to disappear on its own.