FAIRY RINGS
Fairy rings usually appear in a lawn as
circles or arcs of
dark green, faster growing
grass. A ring of thin,
dead, or
dormant grass
may develop both inside and outside this circle or arc. They vary in size from a few
inches to 50
feet or more in diameter,
but most are 3-15 feet across.
Fairy rings are
caused by soil organisms that decay organic matter under the soil surface, i.e, tree
stumps, large roots
and buried construction
lumber. The fungus spores grow
and spread throughout the
soil, sometimes to a depth
of a foot or more, forming a
dense, white, thread-like
network which has a strong,
musty odor.
In mild weather, following rains or heavy irrigation a large number of mushrooms or puffballs (the fruiting bodies of the fairy ring fungi) may suddenly appear in the circle or arc outlining the fairy ring. The lush, dark green grass of a fairy ring is due to the increased amount of nitrogen made available to the grass roots by the fungus as it breaks down organic matter in the soil. The ring of brown "dormant" grass is caused primarily by temporary exhaustion of soil moisture and possibly nutrients. The grass in this area may become so weakened that it succumbs to environmental stresses. It also may be killed by other diseases and invaded by weeds. The severity of the problem may vary from year to year.
The control of fairy rings is very difficult, as the soil becomes almost impervious to water. There are two ways to combat a fairy ring problem - suppression and eradication. Suppression is accomplished by masking the symptoms by forcing large quantities of water 10-24 inches deep into the soil, at one foot intervals, in the rings of dark green and thin or dead grass. This should be done at the first sign of wilting grass, using a tree-feeding lance or root-feeder attachment on a garden hose. Fairy rings can only be eradicated by one of two ways; fumigation (which should only be performed by licensed, professional pesticide applicators), or the removal and replacement of all the infected soil. Both methods are laborious, costly, and not always successful. The soil removal should be done by carefully digging out and discarding all infected soil in the ring area. This should be done 12 inches or more deep and about 4 feet wide, including at least one foot beyond the outermost evidence of infection. Your tools should be sterilized with alcohol before replacing the soil removed with fresh, clean soil.
Agro-Lawn has found that in most cases, the only cost-effective way of dealing with the problem is to mask the damage symptoms caused by the fungus. This is accomplished by re-seeding of the thin or dead areas.
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