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Controlling Brown Patch in the Lawn

Brown Patch is a major disease that affects warm turf grasses in our area. The disease is most prevalent between November and May when temperature is below 80-degree.

Fahrenheit.Turfgrasses such as St. Augustine grass, zoysiagrass and bermudagrass are susceptible to this brown patch disease. Excessive nitrogen fertility levels and thatch often lead to outbreaks of brown patch.  The disease first appears in lawns as small, circular, brown areas several inches in diameter which may then quickly increase to 3 to 6 feet across. These areas often grow together, forming irregular patches of brown, blighted turf up to 20 feet in diameter. The foliage often wilts and collapses, giving the blighted patches a sunken appearance. The base of the grass close to the soil turned brown, water soaked, and the blade can easily pull from the base. Damaged turf usually recovers when conditions no longer favor the spread of the disease. Regrowth of the turf usually starts in the center of the blighted area, forming a ring. Weeds may invade turf damaged by brown patch. Damage may result in the death of the foliage, stems, stolons and roots

Control Measures-Nitrogen fertility has a significant impact on brown patch development. High nitrogen levels promote the growth of soft, succulent leaves that are susceptible to attack by the brown patch fungus. To help prevent disease outbreaks, apply a low rate of a nitrogen fertilizer at eight-week intervals or use a slow-release nitrogen source to maintain an even growth rate. To reduce disease outbreaks during the late winter and early spring, avoid fall applications of nitrogen fertilizer. During periods of active disease infection, curtail all applications of nitrogen as nitrogen encourages further spread of the disease. Finally, maintain phosphorous and potash levels according to soil test recommendations.

Moisture also plays an important role in disease development. Good drainage is needed to remove excess water. To speed evaporation of water from the foliage, prune nearby trees and shrubs to reduce shade and improve air movement. Also, irrigate lawns early in the morning and before 10 am, not in the evening. This will prevent prolonged wetness of the foliage.

Thatch often harbors the brown patch fungus. Periodic mechanical dethatching or core aerification is needed to prevent thatch buildup, especially on St. Augustinegrass and zoysiagrass lawns. Outbreaks of brown patch occurring on thatch-heavy lawns are likely to reoccur and cause damage in following years unless the thatch is properly removed.

Apply fungicide as soon as brown patch symptoms appear and continue until the turf starts to recover or until weather conditions such as wetness no longer favor the spread of disease. For effective control, follow the fungicide label directions. The time interval between applications varies between 10 to 21 days, depending on the fungicide used. Keep in mind that, not one, but several applications of a recommended fungicide may be necessary to adequately control brown patch. Also, for effective control, rotate pesticide after every 2 to 3 applications. For more information on brown patch and other related horticulture topics, contact Grantly Ricketts with UF/IFAS Extension at gricketts@ufl.edu or 321-697-3000.

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