I have a lawn that has this fungus. I thought it was powdery mildew and pythium blight. but it is an odd time of year for it. It has been unseasonalbly warm in the mid 60s and very wet. The local grange said it was slime mold but I find that hard to belive since the blades of grass are spotting and turning brown.. Sorry about the picture it is the best one I could get.