dark green circles

[flowerlover]

We have an odd pattern appearing in our Bermuda lawn for the second year now. There are dark green circles with an average diameter of 2 1/2 feet mainly on the front and sides of our 3/4 acre lot. There are about ten of these.
Does anyone know what could be causing this? :?

[Billusa99]

Well, at first thought, I would make a pointed hat out of tinfoil, crack a cold one and wait in your lawn chair for Mel Gibson and the aliens to arrive at those "signs." :lol:

But, it actually sounds like fairy ring, a fungal disease. I would spread corn meal (a natural fungicide) on it and the surrounding healthy areas and water in, once per week, till it is gone.

[flowerlover]

Never heard of that, but I've not heard of lots of things, I'm finding out! We'll try the cornmeal.
Thanks!

[Billusa99]

I have not seen it myself down here, as I have St. Augustine. it is a common problem in more norther climes, where I used to live, with Bermuda and Zoysia.

Here is an excerpt from U. Nebraska, which is obviously not "organic" but fills in some blanks as to what you may have:

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An information note from the University of Nebraska has provided me with new ideas regarding fairy ring, a common disease problem on warm season turf.

Fairy rings may appear as 1) mushrooms in circles, lasting for only a brief time; 2) a dark green ring or circle of grass with or without mushrooms; 3) arcs or circles of dead grass with green grass inside the circle, with or without mushrooms present. The circles tend to get larger from year to year.

Four options for control are suggested in the information note:
1) Prevent the problem by removing tree stumps, large roots, construction debris and other organic matter prior to establishing a new lawn.
2) Pump large quantities of water 10-24 inches deep into the soil at 1-foot intervals within the ring, and up to 2 feet on either side. This could be accomplished by using a tree root feeder. The reason for pumping water into the ring is that the fairy ring fungus damages grass primarily by interfering with water movement into the soil. Maintain adequate nitrogen fertility, but don't overdo it.
3) Eradicate by removing the sod in a zone 2 feet on either side of the dead (or as the case may be, dark green) ring. Go to a depth of 12-18 inches, or a few inches below the white mycelial mat if this is visible. Don't spill any infested sod or soil on healthy turf. When excavation is complete, fill the trench with fresh topsoil and replant. Obviously this only makes sense when you have one or two very small fairy rings. And there's certainly no guarantee that it will work.
4) If several fairy rings are present, you can attempt biological antagonism. Spray a non-selective herbicide such as glyphosate (Roundup, others) to kill the grass over and adjacent to the fairy rings.

After the turf has died, strip the sod and rototill the entire area in different directions to thoroughly mix the fungal mycelium from different rings. Fairy rings will not move across or overlap each other, and when occupying the same site, they will tend to eliminate each other. Just imagine - hostile factions of fungi battling each other to the death! Note that these four suggestions for dealing with fairy ring do not come with any guarantees. But they are worth trying depending on the severity and circumstances of the problem.
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[Dchall_San_Antonio]

Or you could sprinkle corn meal on it and be done with it.

I've seen circles 30 feet in diameter at the McNay Art Museum in San Antonio.

[flowerlover]

So if we don't do anything the circles will meet someday and our yard will be that nice dark green? Seriously, if left untreated for years, what would happen? Not that we won't treat it - just curious...

[Billusa99]

No... use the corn meal as I suggested up top. It is a fungal disease/infestation.

If you Google 'fairy ring fungus' you will see pictures of later stages, where the rings brown out... not pretty.