Brown Patch Disease of Turfgrass

Brown patch of turfgrass is caused by the fungus Rhizoctonia solani Kuehn. All commonly cultivated turfgrasses in Nebraska are affected by this disease, but differences in susceptibility exist within cultivars of the various turfgrass species. Primary hosts are bentgrass, perennial ryegrass, tall fescue and annual bluegrass. Certain species of Rhizoctonia are capable of attacking turfgrass plants from seedling stage to mature plants and are pathogenic over a wide range of environmental conditions. In some literature, brown patch may be referred to as Rhizoctonia blight. In zoysiagrass, it is referred to as large brown patch. 

Symptoms

Figure 1. Roughly circular patches typical of brown patch on taller-cut turfgrass.

Figure 2. Irregularly-shaped leaf spot of brown patch (right) and bleached leaf spot of dollar spot.

Figure 3. Brown patch symptoms on a bentgrass green.

Figure 4. Spread of brown patch by mowing.

On home lawns, golf course fairways and similar turfs, field expression of the disease is the presence of roughly circular patches of dead and dying grass (Figure 1). Diseased areas may encompass large portions of the turf. Turf with these patches appears somewhat "sunken." The grass in the center of the diseased patches may be less affected, giving the appearance of the "frog-eye" symptom commonly associated with summer patch. However, the presence of the characteristic brown patch leaf spot on individual blades should distinguish it from this disease. Also, the affected turf appears less matted than that affected by summer patch.

Green plants within the affected turf have grayish-colored leaf spots that are long, irregularly shaped and surrounded by a dark brown margin (Figure 2). Diagnosis of brown patch should be made not only on the characteristic leaf spot symptom, but also should include gross symptomatology of the affected turf, and, in some situations, culturing of the pathogen.

On bentgrass greens, symptoms appear as roughly circular, reddish-brown patches that vary in size from 6 to 8 inches to a foot or more in diameter (Figure 3). Infected grass blades first appear water-soaked and purplish-green. They soon die and turn light brown. Occasionally, a grayish "smoke ring" 1 to 2 inches wide and composed of wilting, webbed grass blades marks the advancing margin of the patch. The smoke ring is best observed in early morning while dew is present.

Disease Cycle

Factors Favoring Brown Patch

Integrated Disease Management

• Avoid heavy, early spring and summer fertilization, particularly with soluble nitrogen.

 

 

• Avoid over fertilization of turfgrasses growing in shaded areas.

 

 

• Use slow-release nitrogen fertilizers. Fertilize to maintain adequate but not lush growth during the growing season. Properly fertilized turf will recover quicker from disease injury than will under-fertilized turf.

 

 

• Remove and dispose of clippings from infected areas or when conditions are conducive to disease development. Mulching mowers that chop clippings to 1/4 inch or less do not contribute to brown patch development.

 

 

• Prune woody landscape plantings and trees to allow better air movement and light penetration to reach the turfgrass canopy.

 

 

• Water infrequently, but deeply, in the early morning, and avoid late evening and night watering.

 

 

• When available, plant turfgrass cultivars with a known level of resistance to brown patch.

 

 

• Use a preventive fungicide program on high-value turfs with a history of brown patch. On other turfs, apply a registered fungicide at first evidence of the disease. Integrate fungicide treatments with other management practices to maximize their effectiveness.

 

 

• Provide good surface and subsurface water drainage to reduce humidity in the turf canopy.

 

 

• Manually remove dew in early morning by dragging a garden hose or rope laterally across the grass.

 

 

• Annually aerify to reduce thatch buildup.

 

 

Table I. Fungicides for the management of Rhizoctonia brown patch.*

Electronic version issued August 1999
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