Causal Agent:
Rhizoctonia solani
Susceptible Turfgrasses:
Bentgrass
Perennial ryegrass
Tall fescue
Identification:
Brown patch typically appears as circular spots or patches that range in size from 3 inches to over 3 feet (7.5 cm to 1 m) in diameter. These spots can develop almost overnight. Key identifying characteristics include:
Grayish foliar mycelium (fungal growth) visible on the turf.
Grayish-black "smoke rings" often visible in the early morning.
In tall fescue, distinctive chocolate-brown lesions are common.
In other turf species, symptoms may include brownish blighting or leaf twisting.
In Kentucky bluegrass, look for brown "banding" lesions, especially in shaded, wet areas.
Favorable Conditions:
Brown patch thrives under the following conditions:
Temperature Range:
Daytime temperatures between 75°F and 85°F (24°C to 29°C).
Nighttime temperatures above 63°F (17°C).
Weather: Warm, humid conditions.
Contributing Factors:
High Humidity: Prolonged periods of moisture on turfgrass blades.
Excessive Thatch: Layers of thatch retain moisture and create a favorable environment for disease development.
Poor Soil Drainage: Standing water or poorly drained soil exacerbates the risk.
Over-Fertilization: Excess nitrogen promotes lush growth, making turf more susceptible to infection.
Management Tips:
Improve Drainage:
Aerate soil and manage thatch to enhance water infiltration.
Water Management:
Water deeply but infrequently, and avoid nighttime irrigation.
Pre-dawn irrigation that "knocks-down" mycelium has been shown to reduce brown patch severity.
Balanced Fertilization:
Avoid excessive nitrogen applications during warm, humid periods.
Use mostly slow release nitrogen sources in fall.
Air Circulation:
Promote better airflow by trimming trees or reducing shade where possible.
