No matter what type of lawn you have, fairy rings can be a risk. You've probably seen these distinctive shapes on other grassy areas. They're visible as rings of lush grass, sometimes with mushrooms and puffballs, sometimes with a ring of dead grass round the inside. Occasionally mushrooms and puffballs appear on their own. This won't cause any serious damage but it can ruin the appearance of a nicely kept garden.
Because the main organism producing a fairy ring is underneath the ground, you can't eliminate this lawn disease just be pulling up the mushrooms or attacking them with a mower. Fungicide generally won't penetrate deep enough - it can get rid of the symptoms, but only temporarily. It's possible to dig up the entire structure, digging to at least a depth of 1 foot and a width of 2 feet on either side of the ring, and disposing of the affected soil well away from your garden - but even then, after you've reseeded or laid new turf, the fairy ring sometimes returns.
If you can't kill fairy rings, the next best thing is to learn to control them. Sometimes you can slow their growth by exposing them to organic matter taken from another fairy ring, as each fungus produces chemicals to inhibit the growth of rivals. You can also try making holes at least six or seven inches deep into the soil all around the ring, then mixing a small amount of household soap or washing-up liquid into water and using it to irrigate them heavily every other day. This will nourish the roots of the dehydrated grass and help it to fight back.
You can also attempt to mask the symptoms of fairy rings by closely mowing the lush grass they produce or by adding fertilizer to the unaffected parts of your lawn so that the grass is lush all over.
Fairy rings can often be avoided, and can certainly be controlled, with proper lawn care. Read our other lawn care advice pages to learn more about how to keep your lawn grass healthy and resilient.