Monday, June 20, 2016

Basidomycetes?, Mushrooms?, a Dancining Fairy?...

After many recent calls about mushrooms the last few weeks, I want to update a question asked to me over 10 years ago.

After reading your articles for several years now, I’m going to give you a shot at my problem.  I have these perfect circles in my yard.  Sometimes there are mushrooms growing in the circle and other times they are just green grass followed by a dead area then green grass again.  The circle looks like a halo or a ring around Saturn.  The dead areas are just a little band about six inches around the circle.  These circles are amazing because you could take a compass, and they appear to be perfect circles.

I know you have helped out many people including myself in the past, any ideas on this problem?

Will you be offended if I tell you that you have fairy ring?  It is amazing how nature produces these perfect circles!  There are myths about these rings going back to medieval times.  When I was in college (also the dark ages!), the only control for this fairy ring was to dig up all the soil up to 20 ft. deep and replace it.  Luckily science has advanced since then.

A fairy ring, in the old days, was believed to be where a fairy danced around in your yard.  It is actually caused by decomposing organic matter either in the soil or in the thatch.  There is a certain class of fungi (Basidomycetes) that are responsible for the rings that you see. 

You described in your question the damage very accurately.  You have a band of green grass and a band of dead grass then the center of the circle is usually green, next to the dead area, and then just regular color in the middle.  Under ground, the fungus is sending out mycelium which are root like structures of the fungus that grow in a dense mass.  This mass doesn’t allow water to penetrate it (think of a real pot-bound plant when you water it and all the water goes to the outside edge of the pot and runs down the edges and out of the holes in the bottom, without really wetting the plant).  The mycelium mass is hydrophobic (water hating), this results in the dead ring that you see above ground.  The turf in this area is not getting any water.  Also the mycelium are constantly sloughing off and dying and as they break down in the soil, they release nitrogen.  This nitrogen can be in toxic levels, resulting in the dead areas.  Next to the dead areas, the nitrogen causes the areas to be dark green.  Think of an area where you have seen a dog urinate.  You have a dead area from too much nitrogen, then a green halo where the nitrogen levels are ok for the grass.  The mushrooms are just a fruiting body of the fungus that you see at different times of the year.  It is amazing how they are in a perfect circle. 

To control fairy ring, unlike 20 years ago, you don’t have to dig up your entire yard.  A good cultural practice is to apply a wetting agent, then aerate, and then reapply a wetting agent.  If that doesn’t give you satisfactory results, you can also put out a wetting agent, aerate, drench in a fungicide including a wetting agent, and see how your results are.  It may take several cycles of this treatment to be effective.  Heritage fungicide (derived from a mushroom), Fame and Pro-Star are fungicides that are labeled to control fairy ring.  Always read and follow product label.

It is truly amazing how Mother Nature creates these perfect circles.  However, I don’t believe many golf course superintendents are praising her when these circles show up on their golf green.