Fairy rings are appearing throughout the eastern and Midwestern United States.  In many situations the typical dark green circle is quite apparent.  In some areas continual rain beginning this spring through the summer probably has leached some nitrogen from the turf making the rings more evident.  Fairy rings are categorized as 3 types.  Type 1 rings exhibit a zone of dead grass, with one or two zones of darker green grass and badidiocarps.  Type 2 rings exhibit a single ring of darker green with basidiocarps.  Type 3 rings appear as circular arrangements of basidiocarps, and they have no visible effect on grass growth.  In all cases the basidiocarps are produced briefly. 

Controlling fairy ring is difficult and in most cases masking the symptoms with nitrogen applications is the best alternative.  This is especially true with Type 2 and 3 fairy rings.  In areas where fairy ring is prevalent, check the amount of thatch or organic matter present.  If considerable organic matter is present aggressively try to reduce the amount present through coring and topdressing.  If control is desired there are fungicides labeled for control.  Greater success with fungicide applications is achieved through coring prior to fungicide treatment and then drenching.