BROWN PATCH

brown patch leaf lesions	Characteristic	Description
	Host Grass Species	bentgrass, bluegrasses, fescues, ryegrasses
	Month(s) with symptoms	May to September
	Stand Symptoms	patches (4 inches to greater than 3 feet)
	Foliar Symptoms - Location/Shape	leaf lesions
	Foliar Symptoms - Color	tan, brown, or yellow
	Root/Crown Symptoms	none
	Fungal Signs	mycelium or none

 

Note: Still not sure if this is the right disease? The Turfgrass Disease Identification program may be helpful. Or consult the experts at the Turf Diagnostics Lab. Check the TurfFiles glossary for definitions of unfamiliar terms.

FACTORS AFFECTING DISEASE DEVELOPMENT

Brown patch is most severe during extended periods of hot, humid weather. The disease can begin to develop when night temperatures exceed 60°F, but is most severe when low and high temperatures are above 70°F and 90°F, respectively. The turfgrass leaves must be continuously wet for at least 10 to 12 hours for the brown patch fungus to infect. Poor soil drainage, lack of air movement, shade, cloudy weather, dew, over-watering, and watering in late afternoon favor prolonged leaf wetness and increased disease severity. Brown patch is particularly severe in turf that has been fertilized with excessive nitrogen. Inadequate levels of phosphorus and potassium also contribute to injury from this disease.

CULTURAL CONTROL

Varieties of tall fescue vary widely in their susceptibility to brown patch. Selection of a tall fescue variety with a high level of brown patch resistance is a critical first step in any management program. There are few differences in brown patch resistance among varieties of bluegrass, ryegrass, or bentgrass. Do not apply excess nitrogen when conditions favor disease development. In general, cool-season grasses should not receive more than 1 pound of nitrogen per 1,000 square feet at any one time. Avoid applying nitrogen to cool-season grasses in late spring or summer, or use very low rates (0.25 lb N/1000 ft² or less) if necessary.

Ensure adequate amounts of potassium and phosphorus by applying these nutrients based on soil test results. Avoiding prolonged periods of leaf wetness will drastically reduce the severity of brown patch. Leaf wetness can originate from irrigation, dew, or guttation (which is the water that is sometimes exuded from turfgrass leaves during the night). To minimize leaf wetness, do not irrigate daily. Instead, water deeply and infrequently, every 3 to 4 days to a depth of 6 to 8 inches. The timing of irrigation is also critical; it is best to irrigate early in the morning, just before sunrise. This removes large droplets of dew and water from the leaves and speeds drying of the foliage after sunrise. Avoid watering after sunrise or in the late afternoon or evening, as this will increase the duration of leaf wetness. Proper landscape design and site preparation can help to minimize brown patch problems. Turf surrounded by trees, shrubs, buildings, or other barriers will remain wet for extended periods of time due to reduced air movement and sunlight. Removal or pruning of trees and other barriers will help minimize leaf wetness and discourage brown patch development. In shady areas, plant turfgrass species that are tolerant of low light levels, such as hard fescue, chewings fescue, or strong creeping red fescue. Good surface and soil drainage will also help reduce the incidence of this disease. Avoid establishing turf in low areas that collect water or in soil that is heavily compacted. Aerate high-traffic areas each fall to reduce compaction and maintain soil drainage. In golf course turf, daily removal of morning dew can help reduce brown patch development. This can be accomplished by mowing, dragging a hose, or by whipping the greens with a bamboo or fiberglass pole. Golf course putting greens should be cultivated regularly to maintain soil drainage and aeration.

CHEMICAL CONTROL

Fungicides are effective for brown patch control, and can be applied on a preventative or curative basis. Curative applications may not be effective during periods of hot weather because the cool-season grasses are growing slowly and are unable to recover from the damage under these conditions. Consider a preventive fungicide program for tall fescue and creeping bentgrass when conditions favor disease development. For best results, preventative applications should be initiated in the late spring or early summer when night temperatures consistently exceed 60°F.

© North Carolina State University. This information sheet was prepared by Lane P. Tredway, Gail G. Wilkerson, Bridget R. Lassiter, Jenifer J. Reynolds, and Gregory S. Buol. Departments of Plant Pathology and Crop Science, College of Agriculture & Life Sciences, North Carolina State University. Prepared March 23, 2009. Available on-line at www.turffiles.ncsu.edu. This publication was made possible through a grant provided by the Center for Turfgrass Environmental Research & Education (CENTERE) whose purpose is to support worthwhile projects that will benefit both the private sector and the public, and protect the environment.