I have read that this stuff (or yellow variations of it), is harmless. It is not. According to Professor Roy Watling this ‘Dog’s Vomit Fungus’ fuligo septica has spores that can enter the pores in your skin and cause VERY NASTY THINGS to happen there. It has appeared in my grass in Autumn (Fall). If you get it, don’t mow it or touch it. Use a plastic bag over your hand and do that dog-poo thing with it. Tear up the grass to lift it up. Bag it and bin it. Best not to breathe while you are doing it. And wash your hands, of course. Here endeth…. etc.