Brown Spots in the Lawn
Brown spots in the lawn can be attributed to a number of causes, the four most likely being: poor irrigation coverage, disease, dog urine injury or insect/mite damage. Cumulative stress due to irrigation coverage problems often presents itself as brown spots in the mid-summer lawn. If the coverage problem isn’t corrected, turf vigor will decline in these areas after a few growing seasons – eventually resulting in thin or bare, weedy spots in the lawn.
Round, brown spots (often with a greener, “frog-eye” center, and a yellowish outside ring) ranging from 6 inches to 2 feet across in bluegrass lawns often indicate necrotic ring spot (NRS)disease. Late season nitrogen fertilization (apply at least 1 pound of N per 1000 sq ft) will encourage recovery in NRS-affected lawns and is a better alternative to heavy spring nitrogen fertilization (which encourages NRS activity).
The salts in dog urine result in varying degrees of burn from slight discoloration to complete death. Irrigation that dilutes urine to a less concentrated nitrogen form causes a ring of rapid grass growth around the spot. Lawns suffer the most damage in hot, dry weather and under minimal irrigation. The best solution to this problem is training the dog to use a less conspicuous area of the lawn, or a graveled/mulched area in the landscape.
Clover mites can also cause brown spots in summer. In lawns with a history of mite problems, irrigate as long as possible in the fall (without endangering irrigation system components), and winter water. The best prevention and cure for winter mite activity is irrigation to prevent extreme winter dryness.
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Updated Monday, February 24, 2014