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Rhizoctonia Brown Patch

Brown patch is a fungal disease caused by Rhizoctoniaspecies. It commonly occurs in hot, muggy weather when night temperatures are at least 70°F and daytime temperatures are in the 80s and 90s. It is favored by heavy rains or watering and by grass that is dense and at least adequately fertilized.

The disease appears as patches up to two or three feet wide. The patches may be dark blue initially, as though under drought stress. The color quickly changes to purple-brown and then light brown. The patches may develop green centers and resemble summer patch or necrotic ring spot. In light infections, the turf generally recovers in two or three weeks. When the attack is severe, the crowns, rhizomes, stolons, and roots may turn brown and rot, causing turf to be thinned or killed in large areas.

A few cases of brown patch have been confirmed at the Plant Clinic. Many similar cases have been caused by drought, not a pathogen.

Brown patch can be prevented with the cultural practices listed in Report on Plant DiseasesNo. 411. Once the disease occurs, chemicals may keep it from spreading, but long-term control requires following cultural recommendations. Chemical options are listed in the 1997 Illinois Commercial Turf and Landscape Pest Management Handbook.Be sure to read the label on the selected product for recommended formulation, rates, and timing for your particular turf conditions.

Because such applications usually require sprays at five- to fourteen-day intervals throughout the summer, fungicide control of brown patch is usually reserved for golf courses. Products are not always available in quantities suitable for homeowner use. The recommendation for a severe infection in a home lawn is to rake and remove the dead areas, follow cultural recommendations, and re-seed with a blend of resistant turf grasses suitable for the light requirements of the lawn.

Author: Nancy Pataky


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