Fungi are nature’s dustmen. Fungi convert dead organic matter into basic nutrients that re-enter the food chain and are eventually re-cycled. A few mushrooms or toadstools appearing in your lawn is a healthy indication that the fungi in your soil are active, and perhaps breaking down something like an old tree root buried in the soil. The fungi appear on the surface and contain spores which are released into the atmosphere. If your lawn has a heavy concentration of toadstools etc then it may be necessary to treat your lawn. However just a few mushrooms here and there on your lawn will not be harmful.
Helpfull Tip: Picking out any fungi before mowing is a great way to prevent the spread of spores. Remove the fungi from the the stem and dispose of safely after: ALWAYS WEAR GLOVES