Brown Patch

Noticing brown, circular patches appearing in the grass? Well, it probably is just what it looks like: Brown patch. The fungal disease brown patch causes blighting of the turfgrass foliage, turning lawns from pristine and green to splotchy with shades of brown and tan. To gear up for the onslaught of brown patch, we asked Lane Tredway, an associate professor and extension specialist at North Carolina State University, to breakdown brown patch.

Cause and identification. Brown patch is common across the country in full-season grasses. And it is especially prone to grow in warm and humid environments and turf, such as fescue, ryegrasses and bentgrasses, Tredway says. “Brown patch becomes much more common and more problematic as you go further south down into the transition zone where the hot and humid conditions persist for longer periods of time.”

There are a few conditions that make brown patch ripe for forming. The fungus usually begins to grow when the nighttime temperatures are around 60 degrees, Tredway says. Also, its primarily active at night when turfgrass leaves tend to be wet from either dew or irrigation water.  

“The fungus grows and infects the turfgrass leaves in warm and humid weather and, in doing so, it causes a dieback of the foliage,”  he says.

Brown patch appears in circular patches that are shades of brown and tan. In grass, such as tall fescue, the patches range from 6 inches to several feet in diameter.
    
Prevention and control. The key with brown patch is really the ability to manage the wetness and humidity in the turf canopy.  So there are multiple steps that can be taken to prevent and control the disease, from proper mowing and irrigation to actually using fungicides.

“First of all, selecting a variety of turf that has been bred for resistance of brown patch is a very effective way to manage it,” Tredway says, adding a local extension agent or the National Turfgrass Evaluation Program can help with identifying resistant types in one’s area. “In addition, how the turf is mowed, fertilized and irrigated can have a tremendous impact on the development of the disease. And so, turf managers can adjust how they manage the turf to reduce their problems with brown patch.”

Tredway says it’s important to follow the recommended mowing lengths for each grass species. “If you go above that mowing height, then brown patch becomes much more problematic,” he says. “Since the turf canopy is taller and denser at higher mowing heights, the canopy holds humidity and stays wet for longer periods of time, which encourages the development of the disease.”

Irrigation is important for the same reason. Irrigating too frequently allows turfgrass to hold moisture longer and exacerbate brown patch, Tredway says.

Fungicides can be used on both a preventative and curative basis, Tredway says. The most effective products belong to the QoI class of chemistry, he says. Products that contain active ingredients like azoxystrobin and pyraclostrobin.

Other steps to take into consideration in areas where brown patch might grow is the turf planting process itself. The disease is problematic in poorly drained soils and shady areas.

“One thing that is important from a landscape design standpoint is that you’re not trying to grow turf in areas that are pocketed or surrounded by trees or other obstructions because those areas tend to stay wet longer,” he says. “It creates a much more conducive environment for the development of the disease.” L&L
    
The author is an associate editor at Lawn & Landscape. She can be reached at clawell@gie.net.