What’s Killing My Centipede Lawn?
Large patch is the most damaging disease of centipede lawns in eastern North Carolina. Watch for it this spring. It also occurs in St. Augustine, and zoysia. Excessive nitrogen fertility, fertilizing too early or too late with nitrogen, mowing lower or higher than recommended, excessive thatch, poor drainage, excessive irrigation, and/or wet, overcast days in late spring or fall can lead to outbreaks of this disease. High temperatures between 70 and 85 degrees are ideal for large patch development as are soil and thatch temperatures between 40 and 70 degrees.
Large patch is seen as small, circular, brown areas several inches in diameter to up to 2 feet in the spring, but may damage much larger areas up to more than 20 feet in diameter. Damage is often noticed at spring green up. Affected areas do not green up like surrounding grass. These areas often expand in size as temperature warms in spring and summer due to damage sustained over the fall and early spring. Damage to individual stems begins as water-soaked lesions followed by wilt of leaves and eventual browning. When temperatures warm in the summer recovery occurs, but the disease will spread again once favorable weather conditions return.
The best way to prevent large patch is to follow good lawn care practices. Fungicides are a last resort to stop spread of the disease and applications will not immediately clear it up or stop it from happening again. If the conditions and maintenance practices that encourage the disease continue then the disease will also.
Do not apply fertilizers with nitrogen to susceptible warm season grasses before June or after August. Lush growth is perfect for large patch. Water grass only when soil is dry. Most lawns only need water when they begin to show signs of drought stress like curling leaves. Then apply one inch of water.
Thatch, the layer of organic matter on top of the soil in lawns, may make the disease worse if it is more than ½ inch. Prevent thatch buildup by mowing at the proper height for your grass and doing so frequently. Mow to remove only one third of the grass blade. Mow centipede, bermuda, and zoysia to 1 to 2 inches when the grass gets 1.5 to 3 inches tall. Mow St. Augustine to 3 inches when the grass gets 4.5 inches tall. Most grasses need to be mowed every 7 to 10 days when actively growing. Smaller clippings break down quickly and do not cause thatch buildup. Zoysia lawns develop more thatch due to their thickness. Zoysia lawns need to be dethatched or core aerated more frequently than other lawns to reduce thatch.
Provide good surface and subsurface drainage since excess moisture is ideal for disease development. If part of your lawn has depressions top-dress them with sand. Make sure leaf blades of centipede and St. Augustine show through the sand. Topdressing and core aerating is best done from May through August to help surface drainage. In poorly drained soils topdressing with sand may not provide good enough drainage. In those cases it may be necessary to install a drainage system to move the excess water away. In other areas the soil may to too heavy for drainage alone to stop the disease. Bermudagrass is the least susceptible of the warm season grasses to this disease and you might consider switching to it.
In some cases shading from trees causes the lawn to be wet longer than if in full sun. Thinning tree branches, removing lower tree limbs, or removing trees may be an option to improve drying of these areas. Grasses grow best in full sun. Maybe the trees could be left and grass replaced with something else in large patch problem areas created by shade?
Large patch will be visible during April and May. Look for brown circular areas of grass that did not green up completely like other areas. You may see a dark border around the ring of dead grass on cloudy, wet days or early in the morning with dew. The best long-term solution to large patch disease is to have the proper growing environment and cultural practices for the grass you are growing. As a last resort to slow disease spread, two applications of a fungicide containing triademefon or propiconazole (available in homeowner formulations) may be applied two weeks apart in April and May. Follow label instructions closely to ensure proper application. If you don’t think you can treat the area yourself contact a professional lawn care service. Don’t expect miracles with fungicide applications. The damage done will not disappear until the grass can grow back into those areas. Recovery will occur during summer.
If you have questions about your home lawn, garden, landscape, or trees call the Pitt County Master Gardener Extension Volunteers at 902-1705 or email them at firstname.lastname@example.org. Find more gardening info at https://pitt.ces.ncsu.edu.
Danny Lauderdale, Extension Agent