Iris Cohen wrote:

I have gotten a ring on my lawn were there is no grass and the middle is
darker then all the other grass.

These are called "fairy rings." It is caused by a fungus. You need to spray
with a fungicide and possibly remove some shade.

Contrary to this posting, "fairy ring" mushrooms are not harmful to anything
and do not require any treatment. Certainly no need to spray any more toxic
chemicals into the environment. They are the fruiting bodies of a fungus which
assists in the decompostion of woody elements (old tree roots, etc) under the
soil surface. They are temporary in nature, tending to be most prevelent in the
damp, cool temps of spring and will disappear with summer heat. Raking away the
'shrooms will satisfy appearance considerations. Improving soil fertility will
help as well, so consider aerating, thatching and applying appropriate
fertilizer as well.

pam - gardengal