Mushrooms can grow in many different areas of your lawn, including on the stumps of old trees. Unwanted growth of mushrooms can not only adversely affect the appearance of your yard, but can be potentially hazardous to small children or pets who might put them in their mouths. Fortunately, getting rid of them is not hard.
Remove the mushrooms from the old tree stump yourself by picking them off manually.
Scrape the tree stump with a garden tool, such as a trowel, to be sure you have removed all of the mushroom remnants. This will prevent them from growing back.
Apply a fungicide to the tree stump. A fungicide can kill the mushrooms, while not affecting the stump or the surrounding grass. It will also prevent mushrooms that you remove by hand from coming back. Be sure to read label cautions before using a fungicide.
Apply a nitrogen fertiliser to the lawn around the old tree stump to prevent the regrowth of mushrooms. Use the rate of 0.454kg. nitrogen for every 1,000 square feet of grass being treated.