Brown patch in lawn may be sign of disease or stress

Posted June 26, 2014 at 11:43 am

Many Missouri lawns are already showing signs of the disease brown patch this summer according to Patrick Byers, horticulture specialist, University of Missouri Extension.

General symptoms appear as small circular patches of brown, lifeless grass, but specific symptoms vary depending on the turf grass species and mowing height.

These patches often enlarge and reach diameters of six feet or more.

“The most common lawn grass that will show signs of brown patch (Rhizoctonia solani) is tall turf fescue. However, other turf species like zoysiagrass can also be affected,” said Byers.

Grass is most susceptible for brown patch when it is growing vigorously, and daytime temperature range between 75 and 85 degrees Fahrenheit, free moisture is present on the foliage, and night temperatures fall below 68 degrees.

“The fungus can live on dead organic matter in the soil and attack grass when the right conditions arise. Hot, humid conditions promote the spread of the disease,” said Byers.

There are management strategies that can help prevent the disease. For starters, Byers recommends that you fertilize your yard correctly.

“Avoid heavy, early spring and summer fertilization. Then be sure to fertilize to maintain adequate, but not lush, growth during the growing season,” said Byers.

It is a good idea to prune trees and shrubs to allow air movement and light to reach the turf grass. Another way to prevent the diseases is to collect waste.

“Mow only when the grass is dry and remove no more than one third of the top growth. It is best to remove and dispose of clippings from infected areas,” said Byers.

Watering no more than once or twice per week can help prevent the disease from spreading. More frequent watering (or watering at night) provides an ideal environment for disease development.

According to Byers, using a preventive fungicide program, with recommended fungicides, is the final step for the worst cases.

“Some chemical treatments may suppress the disease, but it is not guaranteed. The treatment can be expensive even if you do it yourself,” said Byers.

When making a fungicide application, it is best to treat the entire lawn instead of only the infected areas, according to Byers.

“If only the leaf blade is affected, the grass will come back when growing conditions are more favorable. However, if the disease reaches the crown of the grass plant, it may be killed and must be reseeded in the fall,” said Byers.

For more information on lawn care, contact the University of Missouri Extension Center nearest you or call the Master Gardener Hotline in Greene County, (417) 881-8909.