The clean-up pass is another area susceptible to stress at this time of year. Where possible, consider skipping this final extra mowing for a few days to allow the turf to recover from the past couple of stressful weeks. Many courses have sponsored tournaments in these weeks which require extra mowings and extra golfers. A temporary raising of mowing height can go a long way to help turf recover. Many golf course superintendents are reporting fairy rings.
Most reports are of extra green rings without turf injury.
Keep in mind that the fungi that cause fairy rings are saprophytes that get their nutrients from dead organic matter and do not attack turf directly. In the process of degrading organic matter, nitrogen is released which fertilizes the turf resulting in the green ring. Fairy ring occurrence varies a lot from week to week and from season to season. It is often associated with excess thatch, but can also occur in sand-based greens. If the extra green ring is the only symptom, try masking it with iron.