The warm weather here in the south left a breeding ground in my yard for the biggest mushroom EVER! The good thing about mushrooms is that, while they may be ugly, they are not usually detrimental to a lawn. Mushrooms usually grow from the presence of dead organic matter and high moisture in the lawn. Dead organic matter that supports mushroom growth is often manure, thatch, sawdust and plant debris like leaves, needles, bark or stumps.
There are no confirmed chemical treatments for mushrooms; although, you can perform control measures to help reduce their appearance in your lawn. First, inspect your lawn during periods of high rain and pick the mushrooms as soon as they begin to grow. Picking the mushrooms will not remove the fungi that allow them to grow, but it reduces the number of spores that spread from the mushrooms to other areas of the lawn.
You can remove or treat the dead organic matter using a garden trowel, shovel and aerator. Remove a section of grass that is deep enough to reach through the lawn thatch and into the soil. If the thickness of the thatch and fungal mat is less than three inches thick, simply treat the lawn with an aerator. You can repeat this process several times each year to promote air movement, which will help to reduce the thatch and dry the lawn by allowing water to penetrate through the grass into the soil.
If your lawn has buried wood or extremely thick thatch, you can fully remove the material with a shovel. The fungus cannot thrive if you remove the source material for their growth. In addition, the water drainage will increase through the grass and dry soil when you remove the thatch and wood, inhibiting mushroom growth. If removing the thick thatch or the wood is impossible, apply nitrogen to the area to help break down the material. Once the fungal source is completely decomposed, you should see a decrease in the appearance of our friends, the mushrooms.