Chlorothalonil or Maneb may be used. Read and follow label directions. Limestone can neutralize the salt that causes the spot or water well and fertilize to promote new grass to grow there. Puffballs or toadstools are present. Fungus grows in organic matter, such as decaying roots etc.
Area is too wet.
Too much organic matter may aggravate. Break mushrooms with rake or lawn mower. Green velvety growth in shady areas. Rake out dead moss. To prevent moss Improve soil aeration.