Extension

With all the rain in Oklahoma, homeowners are struggling to keep up with lawn mowing, but they also need to keep an eye out for brown patch disease.

 

Brown patch is a common fungal disease that shows up on cool-season turfgrasses, especially tall fescue. However, it has been known to appear in hybrid bermudagrass and zoysiagrass, too. Symptoms include circular patches of brown or tan grass, and it can have a dark border. The patch can range in size from a few inches up to 3 feet in diameter.

 

Brown patch usually occurs in hot, humid weather in which the nighttime temperature is above 60 degrees Fahrenheit. It’s especially problematic when foliage remains wet for long periods. Other culprits include poor air circulation, compacted soils and heavy dew. The application of high rates of nitrogen and/or deficiencies of phosphorus and potassium can increase disease severity. In addition, excessive thatch, mowing when wet and leaf fraying by dull mower blades can enhance the severity of brown patch disease.

 

Like most landscape issues, control starts with good management practices. When environmental conditions favor disease, avoid applying excessive rates of nitrogen. Fertilizer should be applied judiciously, and adequate amounts of phosphorus and potassium are essential to ensure the highest possible levels of plant resistance. In general, cool-season turfgrasses should not receive more than one pound of actual nitrogen per 1,000 square feet at any one time. Use very low rates or avoid applying nitrogen in late spring or summer to cool-season turfgrasses. In a typical home lawn situation, the last application of fertilizer in the spring should be applied no later than early May. We are past that point on the calendar, but it is something to note for next season.

 

While we can’t control the rain, gardeners can reduce prolonged leaf wetness by watering infrequently to a depth of 6 to 8 inches at a time. Try to avoid watering in the late afternoon and evening. Removing unwanted vegetation, along with selective pruning, will help improve airflow.

 

Make sure mower blades are sharp, which will reduce damage to the grass. If an area of grass with brown patch disease is mowed, quickly collect and dispose of the clippings on infected areas. Don’t add those clippings to a compost pile. Instead, dispose of them in the trash.

 

In severe cases of brown patch disease, applications of fungicide may be necessary. A preventative fungicide program should be considered in areas that are favorable for disease