Caring for Damaged Centipede Lawns
Many centipede lawns in southeastern North Carolina have suffered serious damage this past winter due to cold injury. These damaged lawns contain large areas of dead grass that never greened up this spring or, in some cases, large areas of exposed soil where the grass has died and completely disappeared. Two symptoms that distinguish damage caused by cold injury rather than insects and diseases are: 1) that large scale damage occurred within the last year – in many cases these lawns were healthy last summer but this spring large areas of lawn, sometimes several feet across, never turned green or the grass is totally gone; and 2) the problem is not spreading – the areas that failed to green up this spring are staying the same size, and are not expanding into healthy, green living grass.
The two most common pest problems that would cause damage in centipede grass similar to cold injury are large patch and ground pearl. These problems have slightly different symptoms. Large patch, a fungal disease, starts out as small circular areas of dying grass that rapidly expand within a few weeks to cover large circular patches that may be several feet across. With this disease you will readily notice healthy, living green grass dying. During the summer, areas damaged by large patch will usually recover to some extent. Large patch can be controlled with fungicides applied in the fall and proper turf management. Ground pearl, on the other hand, are small insects that live in the soil and feed on the roots of grass. Their symptoms are usually first noticed as small patches of grass that die and do not recover. Areas of lawn damaged by ground pearl slowly enlarge, expanding by up to a foot across each year. In most cases, nothing will grow back into the affected area except a few weeds, and if you dig into the soil on the edges of the dying areas you will find the insects, which look like small round pearls about the size of a BB pellet. There is no way to treat for ground pearl so if you find them in your lawn your only option is to plant some other type of grass that is more tolerant to ground pearl feeding, such as ‘Celebration’ bermuda or bahiagrass, or plant trees, shrubs or flowering plants.
Repairing Damaged Centipede
To repair damaged areas of centipede lawn, first consider your symptoms. If they are consistent with cold injury, then repairing the areas is a little easier. If you have large patch disease in your yard you will need to plan to treat the lawn with fungicides this fall and make sure you are not over fertilizing or over watering. If you find ground pearl in the lawn you will have to look for alternatives other than centipede grass as listed above. There are a couple of options for repairing damaged lawn areas, including sowing seed, laying sod, or plugging. The first step in each of these is preparing the soil in the damaged areas by raking away any dead grass and tilling and leveling the soil. Centipede grass prefers acidic soil so adding lime to the soil is rarely needed and should only be done if indicated by a soil test report. When deciding whether to sow seed, lay sod or plug damaged areas, the most important consideration is cost. Sowing seed is less expensive but takes much longer to establish a dense lawn than laying sod or plugging.
Sowing Centipede Seed
Centipede seed may be sown from March to July at a rate of ¼ to ½ pound of seed per 1000 square feet of lawn area. If pre-emergent herbicides, such as crabgrass preventers, were applied to the lawn this spring then seed cannot be sown for two to four months from the time the herbicide was applied, depending on which product was used. If other herbicides have been applied to the lawn be sure to check their labeling to find out how long to wait before sowing seed. For most herbicides it is necessary to wait three to four weeks before sowing seed. Once the soil is prepared, evenly spread seed and press them into the soil surface to ensure good seed to soil contact, which is crucial for germination. Centipede seed take two to three weeks to come up, during which time it is essential to keep the surface of the soil moist. The best way to do this is to water the area lightly for five to ten minutes, two to three times each day. Heavy watering is not necessary since the seed are only at the soil surface. As the seeds germinate and begin to grow, watering should be adjusted to less frequent and deeper applications. No herbicides should be sprayed on the newly seeded areas for at least eight weeks. A low nitrogen, high potassium fertilizer, such as 5-0-15, can be tilled into the soil at seeding and broadcast six to eight weeks later at a rate of 10 pounds per 1000 square feet.
Laying Sod or Plugs
The best time to lay centipede sod or transplant plugs is also March through July. Plugs are simply small pieces of sod that are planted into prepared soil. They can be made by cutting sheets of sod into smaller pieces, as small as 3” squares, or can be transplanted from areas of healthy lawn. When establishing new sod or plugs, keeping the top few inches of the soil moist for the first few weeks is essential to encourage new roots to grow. Watering and fertilization recommendations for sod and plugs are the same as for seeding.
Preventing Future Damage
Prevent future damage to centipede lawns by mowing low, at 1” to 1 ½”. Mowing higher encourages centipede rhizomes to grow above soil level, making them much more prone to winter damage. In addition, do not over apply nitrogen fertilizer. One fertilizer application at a rate of half a pound of actual nitrogen per thousand square feet in mid May is all centipede lawns need. Over fertilizing with nitrogen or fertilizing too early or too late will encourage disease problems, cause thatch build up, and increase cold damage. Have your soil tested to determine if you need to add additional potassium (also known as potash). Potassium is an important nutrient for all plants that helps increase winter hardiness, disease resistance and drought tolerance. Many sandy soils are low in potassium. The only accurate way to find out if your lawn needs additional potassium is to submit a sample of your soil to your local Extension office. In addition, use herbicides carefully. Centipede grass is sensitive to and can be damaged by many common herbicides, especially those used to prevent crabgrass and products containing the active ingredient 2,4-D. . For specific information on centipede lawns please contact me, Mary Hollingsworth, Extension horticulture agent, at the Hoke County Cooperative Extension Center located at 116 West Prospect Avenue Raeford, N.C. 28376 or telephone 910-875-3461.