Fairy rings and lawns: Q?

Richard Winder rwinder at PFC.Forestry.CA
Mon Aug 7 12:44:23 EST 1995

In article <1995Aug6.224849.47263 at cobra.uni.edu>, klier at cobra.uni.edu writes:
>One of the persistent questions in rec.gardens is "there's a 
>fairy ring in my lawn, and it's killing all the grass, how do
>I kill it?"
>My standard answer, based on midwestern experience, is "don't
>bother, the grass comes back better than ever in a few months."
>Nevertheless, there are folks who aver that their lawns never
>recover from fairy rings, requiring replacement of soil and 
>resodding.   Since I don't deal well with spores, 
>I've never made it (AHCHOO!) through an entire mycology course,
>so I'd appreciate some advice from the experts:  Are there
>fairy-ring forming species that are pathogenic or allelopathic
>for common lawn grasses?  If so, what are they, and what controls
>are recommended?

Allelopathic? Yes.  Marasmius oreades is a good example- grass on the
leading edge of the growing mycelium is stimulated, while grass to the
inside dies off.  Although the die-off isn't permanent, the grass in the
center of the ring can certainly be a lot less thrifty for a while.  I'm
not sure why this is- M. oreades is tough, and probably persists to some
degree well inside the ring.  So there could be residual allelopathy, or
it may just be that so much thatch and litter has been consumed that the
growing environment is changed.  You are probably right- patience is probably 
the best cure (for some lawn fanatics, a few months = 1 eternity).  When 
these folks say "never recover", are they refering to the center of the ring,
or its persistence, or the generation of new rings?  If they are merely
referring to persistence, then some fairy rings have been aged at 
several hundred years.  I haven't heard to much about removal methods-
other than the drastic measures you mention.  M. oreades is a delicous
mushroom, so I actually *encourage* it to form in my lawn by inoculating
new parts.  I've seen people on the net encourage people to eat their fairy
ring mushrooms instead of killing them, but they should be properly identified
before doing that (and mushrooms of several species can be growing in the
same ring).  M. oreades has a white spore print, a leathery stipe which revives
in rain (even sun-dried specimens can be harvested), and well-spaced gills 
which are usually notched or free from the stalk.  Clitocybe dealbata is a 
poisonous mushroom which may look vaguely similar, but it usually has 
decurrent gills (persons who don't know what decurrent means should consult
 a field guide before they dive into this!)  There are a heck of a lot of
look-a-likes, so don't use this post as a guide!	-RSW

  RICHARD WINDER                    Title: Research Scientist
  Canadian Forest Service           Phone: (604) 363-0773
  Victoria, B.C.                    Internet: RWINDER at A1.PFC.Forestry.CA

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