Brown spots on zoysia grass are a symptom of a fungal infection. Though brown spots are one red flag indicating a problem, many other symptoms accompany spotted grass blades. Identify how to prevent infection and properly care for your zoysia grass, as well as appropriate control methods, for a healthy, vigorous home lawn.
Providing your zoysia grass with the proper care it needs creates vigorous grass with a greater ability to fight off infection than weakened grass. Grow zoysia grass in full sun to partial shade; excessive shade results in thin growth, according to the Clemson University Extension. Zoysia is a warm-season grass with an ideal temperature range of 80 to 95 degrees F. Collect and rid your lawn of thatch build-up every few years.
Brown patch is a fungal infection of zoysia grass responsible for the presence of brown spots. Caused by the fungus Rhizoctonia solani, brown patch also occurs on other grasses like perennial rye and bluegrass, according to the University of Nebraska-Lincoln Extension. The fungal spores of brown patch thrive in poorly drained soil, warm temperatures that remain over 60 degrees F during nighttime hours, as well as excessively watered and fertilized grass.
Symptoms and Damage
Once infection occurs, symptoms begin with dead blades of grass that create ring-like formations with a diameter of up to 2 feet in the home lawn, according to the University of Nebraska-Lincoln Extension. The grass within the deadened ring is often unaffected and appears healthy. Blades of grass display spots that are a light brown to white color with brown to purple borders. Severe damage may occur if left untreated.
Remove and destroy affected grass after mowing to prevent disease spread. When mowing grass, use a sharp mower blade instead of a dull one; dull blades don't make a clean cut and create wounds that fungi can easily invade. Prevent infection by watering the lawn twice a week in the morning with 1/2 inch of water to avoid creating wet conditions, according to the University of Nebraska-Lincoln Extension.
For chemical control, apply fungicides formulated to control brown patch on zoysia grass. Apply benomyl, chrlorothalonil or another fungicide labeled for this particular use. Through use of a chemical control method, new, healthy zoysia grass will grow and replace the affected grass, though it may take over a month, according to University of Nebraska-Lincoln Extension.