Many Missouri lawns will be showing signs of the disease brown patch this summer according to Gaylord Moore, horticulture specialist, University of Missouri Extension. General symptoms appear as small circular patches of brown, lifeless grass, but specific symptoms vary depending on the turfgrass species and mowing height. These patches often enlarge and join together, reaching 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 such as zoysiagrass can also be affected," said Moore.

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 Moore.

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

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

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

"Mow only when the grass is dry and be sure to remove no more than one third of the top growth. It is also best to remove and dispose of clippings from infected areas," said Moore.

Watering correctly and thoroughly, 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 Moore, using a preventive fungicide program, with recommended fungicides, is a final step for the worst cases. Pesticides registered for use against brown patch include: captan, chlorothalonil (Daconil), iprodione (Chipco), mancozeb, triadimefon and vinclozolin.

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

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

"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 Moore.

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