Question
hi last september i had atree removed dont know what kind exactly left about a 4-5 foot stump end to end it was a big tree got tired of looking at it so i rented a stump remover i didnt totally get rid of all the mulch now sept of this year whenever it rains i get  white patches of tiny what looks like mushrooms. planning on letting ground sink till next spring and add dirt and plant grass seed my concern is are these mussroom type things gonna cause a problem

Answer
These are not a problem. They are the fruiting bodies of a decay fungi that is infecting the roots of the stump and causing the roots to decay. They will not infect anything else so there is no reason to worry. These are a good thing in that the roots are decaying.