Fairy Ring disease

       Anyone who has played golf regularly has seen the disease in the pictures below. This disease is called Fairy Ring.  Fairy ring is particularly prevalent in sandy soils with inadequate moisture and low fertility.

          Fairy ring is caused by a fungus that lives in the soil that feeds on decaying organic matter, ( Items perhaps buried during construction, i.e. tree stumps, roots and logs) The dark green colored circle is caused by an excessive release of nitrogen from the fungus feeding on the decaying matter. The circular shape is caused from the fungi moving outward in search of more nutrients. Preventative and curative options are extremely expensive for the control of fairy ring. We allocate our fungicide budgets to reduce damage from the most important sites on the golf course, i.e. greens > fairways > tees > rough.
      The main causes and cures are well known to turf specialists now, however that was not the case many years ago. There is certainly a fair share of folklore associated with fairy ring.  Here is a website detailing the myths that have been associated with fairy ring over the past thousand years.