Answer: It's difficult to diagnose a turf problem without being able to personally inspect it so I strongly suggest you take samples of the problem to your extension service.
Heavy rains have depleted the nutrients in many lawns. One result is chlorosis, which causes yellow streaks in grass blades. You can correct this problem with applications of iron chelate.
If there's a nitrogen shortage, the blades will be completely yellow. The turf should green up with a light application of nitrogen fertilizer.
Take-all root rot is more serious. Grass blades turn yellow, then die. A circular or irregular-shaped area of affected blades may spread several feet across. Grass thins as the infection spreads. The stolons may be discolored and will pull up easily if the roots are rotted. Regrowth is slow, if at all.
Take-all survives on infested thatch and infected living plant parts. Remove the thatch and don't overwater. Fungicides may or may not help but a top-dressing with sphagnum peat moss one of the best treatments for take-all. Apply two 3.8 cubic-feet bales of peat moss per 1,000 square feet to the affected areas. Soak the peat moss prior to using.
Before doing anything, though, you should take a sample to your local cooperative etension office for on site diagnosis. Best wishes with your lawn.
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