Overview

Brown patch is a fungal disease of cool-season turfgrasses. In higher cut turfgrasses (greater than 1 inch), symptoms are roughly circular patches that are brown, tan, or yellow in color and range from 6 inches to several feet in diameter. The affected leaves will have very unique lesions that are tan in color, irregular in shape, and will often have a dark brown border.

Brown patch is most severe during extended periods of hot, humid weather. Brown patch will become active when night temperatures exceed 60°F (16°C), but will be most severe when low and high temperatures are above 70°F (21°C) and 90°F (32°C), respectively. Poor drainage, lack of air movement, shade, prolonged cloudy weather, dew, over-watering, and watering late in the afternoon all favor prolonged leaf wetness which increases brown patch severity.

Cultural Control

Turfgrass varieties within a species can vary widely in their susceptibility to brown patch, therefore it is a best management practice to plant varieties with improved brown patch resistance when available.

Over fertilization can increase the severity of brown patch. In general, cool-season turfgrasses should not receive more than 1 lb nitrogen/1,000 square feet at any one time. Do not apply more than 0.5 lb nitrogen/1,000 square feet when conditions favor disease development. If applications are kept at or below 0.5 lb nitrogen/1,000 square feet during this time, they will not increase brown patch severity. As always, be sure adequate amount of phosphorous, potassium, and other nutrients are applied based on soil test results.

Reducing leaf wetness periods will greatly reduce brown patch severity. Leaves can become wet from irrigation, rain, dew, or guttation (water exuded from turfgrass leaves during the night). Do not irrigate daily. Instead, irrigation should be applied based on weather conditions and the water requirements of the turf. The time of day that irrigation is applied 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. 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.

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 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.

Fungicides are often available in different formulations. Most of the time they are formulated to be applied through a sprayer, however there are some granular versions available that are applied through a rotary spreader. When in doubt, you can hire a landscape professional to make these applications because they are licensed and trained on how to best apply these products.