What causes a circle of dead lawn grass?

[Egon]

Over in Africa:

Fairy circle (arid grass formation) - Wikipedia

en.wikipedia.org

 

[yozza]

Around here it is mole crickets, the wild turkeys and ducks love it when it rains, causes them to surface.

We get mole crickets in Australia too, Friends often reckon they have a healthy garden because they hear frogs croaking at dark after rain when in fact its often mole crickets. They are ugly looking buggars too (crickets not the friends) attached an interesting link for you and it is American too Mole Cricket damage

 

[Gord Baker]

Perhaps a training circle for a horse? Re SOD it instead of reseeding it.

 

[buckeyefarmer]

Leaking hydraulic fluid will do it.

 

[CloverKnollFarms]

Necrotic ring spot. Good luck. I moved and got a new lawn

The fungus is most active this time of year, so you won’t see it most of the year. It’s a real pain to rid yourself of. At our old home, I treated and tried all sorts of management practices, but it came back most years, and tended to grow in size.

 

[Mikey Z]

Fairy ring mushrooms will grow in a circle and eventually kill the grass

 

[lilranch2001]

I have had fairy rings for 30+ years, but only recently have had mushrooms to go along with them, and mine did not kill the grass, seemingly only stunted it at the place the mushrooms grew

 

[lilranch2001]

Also, this summer we had a very dry early summer and a lot of rain since, and all evidence of fairy rings is missing in my 6 acre lawn as of right now.
One would think that wet soil would exacerbate the “bugs” that cause them