Answer: There are two situations that might have caused the spots in your lawn. The first is easy - dog urine can burn the grass but the nitrogen contained in the urine can quickly green the lawn up, in the center of the spot, leaving a dead ring around it. The second possibility is a fungal disease called Fairy Ring. Fairy rings appear first as circular patches of dark green, enlarging into small circles or circular areas in spring and early summer. Eventually a ring of dead grass develops along the inside of the green zone. Sometimes small tan mushrooms appear. Another green ring often appears inside the dead zone. The fungus (Marasmius) thrives under mild, moist conditions. If the spots in your lawn are caused by animal urine, they will clear up by themselves. If it's a disease, you may need to treat it. Find out for sure by taking a sample of both healthy and affected grass, including the roots and soil, to your local Cooperative Extension office. Best wishes with your lawn!
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