Problem type: Disease
Name of problem: Brown Patch
Plant name(s): Perennial ryegrass, tall fescue, annual bluegrass and bentgrasses are most susceptible. Other species can become infected.
Symptoms / Characteristics:
Roughly circular patches of dead and dying grass, starting off small (1-5" in diameter) and developing into patches up to 2-6 feet in diameter. Patches appear brown with a purplish or grey 'smoke ring' around the edges. Individual leaf blades will have lesions that are irregularly shaped, tan to brown in the center and surrounded by a dark ring at the margin. Turf patches may appear sunken, and the center of the diseased patches may have green tissue, giving it a 'frog-eye' appearance.
Brown patch symptoms can vary, depending on the turfgrass species and height at which it is mowed. Generally the disease moves from a central point, outwards. Distinguishing brown patch from other diseases is by closely inspecting individual leaf blades for the distinct light brown lesions with a dark border. Patches may coalesce to encompass large portions of the turf. Brown patch is caused by the fungus Rhizoctonia solani, which survives and overwinters in plant debris and thatch, remaining dormant until favorable conditions are present. It is very resistant to the environment and can germinate over a wide range of conditions, favoring warm temperatures (>20°C) and humid conditions. Brown patch occurs on dense turf that receives a lot of water and fertilizer in hot weather. Poorly drained soils, thick thatch and night watering allow leaves to stay wet for a longer period of time promoting infection. High nitrogen levels also promote disease development as well as frequent mowing, as the fungus gains entry through wounds.
Control / Preventions:
Avoid over watering which favors fungal development. The best time to water is in the early morning. Avoid late evening and night watering to prevent long periods of leaf wetness. Provide good surface and subsurface drainage. Reduce thatch build up by power raking or core aerating annually. Do not over fertilize. Fertilize for healthy growth maintaining adequate levels of phosphorus and potassium to keep plants healthy to combat disease. Avoid excess nitrogen, but if applying nitrogen, use a slow-release type. Remove and dispose of clippings that are infected with the disease. If possible, improve air movement and light penetration to the area if it is not adequate. Removal of dew in the morning can reduce leaf wetness and can be done by simply pulling a hose or rope over the area.
Chemical control is available but should only be needed on high value grasses. Typically the disease does not usually kill the grass and it may recover slowly. Fungicides can be applied as soon as symptoms are present. Applications can be made at 5-10 day intervals, especially if hot, humid weather is expected. Available fungicides include Daconil 2787, Quintozene and Rovral Green. Read and follow labels carefully for safe efficient control.