Get rid of lawn fungi by pulling up mushrooms as soon as they appear, the San Francisco Chronicle advises. This prevents spore dispersal and the growth of more mushrooms.
Remove any mushrooms that pop up in your lawn, and pick up any pieces before mowing the lawn, as the San Francisco Chronicle recommends. Mowing over mushrooms can spread the spores and create a larger infestation. If they continue to grow back, dig into the soil and pull out any decaying or organic mater on which the fungi are feeding, such as rotting wood. As a last resort, remove the top 12 to 18 inches of soil to get rid of any fungi and spores, and replace it with new soil and grass.
To keep lawns fungi-free, the San Francisco Chronicle recommends raking up and removing loose debris regularly. Fungi feed on decaying matter that often includes fallen leaves and grass clippings. Fungi also need a moist environment, so never over-irrigate your grass. In some cases, water does not drain well, resulting in fungal infestations. Aerate and dethatch your lawn to improve air flow through the grass. Applying a layer of nitrogen-rich fertilizer to your yard also minimizes the spread of fungi.