Where are you and your crop circles? My first thought was lawn grubs. Lift one of those dead patches and examine the roots. If you see white, orange-headed curled creatures, you've got grubs. My second thought was a fungus. You could take photos and send them into the National Enquirer and say little UFO's made them.
Cutworms and japanese chafer beetle grubs often cause those dying circles, so do certain fungi. Try grabbing the dead vegetation and pulling. If it peels up like a loose skin, then it is likely cutworms or grubworms which circle an area cutting off plants from their roots just under the soil or thatch level.
Small circles like that could be from grubs, but what grubs are active in the soil this time of year?
My bet is with fungus. Corn meal is the only solution for fungus disease. As was mentioned, you can control fungus disease with 10 pounds per 1,000 square feet. If you already have the disease, you need 20 pounds per 1,000 to get rid of it.
You can get corn meal cheap at feed stores. Cost is about $5 for a 50-pound bag. You want ordinary ground corn, not corn GLUTEN meal.
