It never fails. The soils start to warm up and the turf grasses are growing well, but there are always a few lawns that are having problems.
There are areas of the lawn that will not green up or the grass is slower greening up. In some cases, the majority of the grass is dead.
What is the problem?
The cause depends on the type of turf grass that is affected. If the grass is centipede, the problem could be winterkill or centipede decline and take-all patch. If the grass is St. Augustine, the problem is most likely take-all patch. For bermuda grass, the problem could be spring dead spot. I have seen all of these problems this spring.
Winterkill or centipede decline is the main reason many people will not grow centipede. With winterkill, the grass looked great going into the winter. In fact, most of these were the best-looking yards the previous summer.
Winterkill is more of a management problem than an environmental or disease problem.
There are several good indicators that centipede could be damaged by winterkill. The first is a spongy feel to the grass. The second way to tell is to pull on the grass. If the stolons move, then the grass can be killed by cold weather.
Winterkill is caused by a combination of factors. The first is mowing height. Centipede should be mowed at 1 1/2 inches high from the soil surface. When centipede is mowed at 2 inches, the stolons of the centipede are unable to root down into the soil. This keeps the roots in the air and the cold weather kills the stolons. The damage from the cold goes to the crown of the grass plant and kills the crown.
Research done at North Carolina State University has shown that centipede with no fertilization and mowed at 1 1/2 inches had 3 percent winterkill. This was compared to centipede with no fertilization mowed at 2 inches that had 25 percent winterkill.
The second factor is over-fertilization, which will increase the amount of thatch in the grass. Thatch can keep the stolons from rooting into the soil. Centipede needs very little fertilizer in a year. The recommended fertilization rate is 1 pound of actual nitrogen per 1,000 square feet per year.
A favorite centipede fertilizer is 15-0-15. To put out one pound of actual nitrogen, 6 1/2 pounds of 15-0-15 should be applied per 1,000 square feet. This can be put out in one application sometime after the first of May, or it can be applied in two applications with half applied in May and the other half in early August.
The third factor is improper irrigation. Light, frequent watering will cause turf grass to have a shallow root system, which makes centipede more susceptible to winterkill. The proper way to water any turf grass is to water deep and less often. In fact, it is best to subject the grass to a little drought stress before watering. Grass that is drought stressed will turn a bluish-gray color. When a section of the grass turns this color it is time to water. Turf grass needs 1 inch of water per week for best growth.
Take-all is a disease that attacks all grasses, but St. Augustine and centipede are attacked most often. This disease attacks the grass in late October and early November. This fungus likes late-season applications of nitrogen. Therefore, the last fertilization should be made by late August. Also, this disease likes soils that have a pH above 6.4.
The symptoms of take-all appear in the spring, but the fungus has already done its damage. To treat take-all, apply a fungicide now and again the first week and third week of October. If the soil pH is high, adding peat moss or sulfur to the soil will drop the pH.
Spring dead spot occurs in Bermuda grass, but is very similar to take-all patch. The symptoms of spring dead spot are small areas, a couple of inches to a couple of feet in diameter, that are not greening up. These areas look somewhat sunken in appearance.
Lawns that have these problems can be corrected a number of ways. If the areas are small, the dead material needs to be removed by raking. This allows sunlight to warm the soil surface, and the surrounding turf will grow over the area faster. Also, aeration will allow the roots of the grass to grow deeper and water to infiltrate the soil easier. If the areas are too large for the grass to cover by mid-summer, then pieces of sod can be laid in these areas to help the grass recover faster.
Increasing the level of potassium, which is the last number on the fertilizer bag, helps the grass plant by increasing drought resistance, disease resistance, and winter hardiness. By proper mowing, fertilization and irrigation, these problems with turf grasses can be reduced.
Charles Phillips is a retired Columbia County Extension Service agent and operates Hort Consulting. He can be reached at cphillipshort@ comcast.net.
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