Saturday, May 31, 2008

Turf - June is the Start of Brown Patch Season in Tall Fescue Turf

June will bring us hot and humid weather. In turf this will mean brown patch disease starting to show up. The following is information on this disease from NC State University.

Brown patch is the most common and damaging disease of tall fescue in Delaware. The symptoms of brown patch are roughly circular patches that are brown, tan, or yellow in color, ranging from 6 inches to several feet in diameter. The affected leaves typically remain upright, and lesions are evident on the leaves which are tan in color, have a dark brown border, and are irregular in shape. When the leaves are wet or humidity is high, small amounts of gray cottony growth, called mycelium, may be seen growing amongst affected leaves in the turf canopy.

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. Brown patch also requires at least 10 to 12 hours of continuous leaf wetness in order to develop. Poor soil drainage, lack of air movement, shade, cloudy weather, heavy 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 have also been shown to contribute to injury from this disease.

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. Current lists of varieties with good brown patch resistance that perform well in Delaware can be found at the National Turfgrass Evaluation Program (

High levels of available nitrogen favor the spread of brown patch. Nitrogen induces tall fescue to produce soft, lush leaf tissue that is easily infected by the brown patch pathogen. Excessive foliar growth also results in a dense canopy that holds moisture and humidity for extended periods of time.

In general, tall fescue should not be fertilized with nitrogen in late spring or summer so as to discourage brown patch development. Following this type of program will result in yellowing and thinning of tall fescue during the summer as nitrogen is depleted from the soil. Turf in this condition is very resistant to brown patch, but may not be acceptable from an aesthetic standpoint. If fungicides are used to protect tall fescue from brown patch, then application of small amounts of slow-release nitrogen (≤ 0.25 lb N/1000 ft2/month) during the summer can help improve the quality of tall fescue turf. This practice, however, will encourage the development of other diseases, such as gray leaf spot and Pythium blight. Tall fescue that is fertilized during the summer should be monitored frequently for these diseases so that they may be controlled before widespread damage occurs.

Avoiding prolonged periods of leaf wetness will drastically reduce the severity of brown patch. Leaf wetness can originate from either irrigation or dew. To minimize leaf wetness, do not irrigate the turf on a daily basis. Instead, water deep and infrequent, 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 guttation water from the leaves and speeds drying of the foliage after sunrise. Avoid water­ing after sunrise or in the late afternoon/evening, as this will increase the duration of leaf wetness. For intensely managed athletic fields, daily removal of morning dew can help to reduce leaf wetness duration and minimize brown patch development. This can be accom­plished by mowing, dragging a hose or rope over the turf, or running the irrigation system for a short time.

Brown patch is particularly severe in soils that are wet and compacted. Providing adequate surface and subsurface drainage, and minimizing compaction through regular aerification, will help to minimize the development of this disease.

Fungicides are effective for brown patch control, and can be applied on a preventative or curative basis. Fungicides vary widely in residual control, or the number of days of brown patch control after application. Fungicides containing the active ingredients azoxystrobin (Heritage 50WG, 0.2 oz/1000 ft2), pyraclostrobin (Insignia, 0.7 oz/1000 ft2) or flutolanil (Prostar 70WP, 2.25 oz/1000 ft2; Systar 80WDG, 3 oz/1000 ft2) consistently provide 28 days of brown patch control, even under severe conditions. For homeowner applications, products containing the thiophanate-methyl are sold under various brand names at garden stores and provide good brown patch control, but these products must be re-applied every 14 days.

Curative fungicide applications for brown patch may not be effective during periods of hot weather because tall fescue does not grow well during these conditions and will recover from brown patch injury very slowly. For this reason, a preventive fungicide program should be considered on tall fescue when conditions are favorable for disease development.

Information from "Managing Diseases of Tall Fescue" Turfgrass Disease Information Note 6 (TURF-006) by Lane P. Tredway, Extension Turfgrass Pathologist, North Carolina State University. Go to the following website for the full fact sheet:

No comments: