My lawn problem is...
MUSHROOMS, CIRCLES OF FAIRY
The presence of mushrooms can be annoying, but they do not damage the lawn. They grow on organic matter in the soil, usually roots, timber debris or decomposing root felts.
Fairy rings, which are produced by many fungi in the soil, weaken and sometimes kill the grass in concentric patterns. They are more likely to grow in soils rich in organic matter or where there is a lot of root-felt accumulation, and they occur more frequently during long dry periods, especially in the summer, following a wet spring. The symptoms of this disease are a ring where the growth of the grass is abnormal, or the presence of mushrooms arranged in an arc. The rings usually grow a few millimeters a year.
Remove decaying residues to reduce fungal growth. To stimulate the new growth of the grass and hide the damage, it is possible to water abundantly and often, to spread fertilizer, to rake vigorously or to ventilate.