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Contributors: J. Baird, Extension Soil Science Specialist, J.R. Baker, Extension Entomology Specialist, S. Bambara, Extension Entomology Specialist, R.L. Brandenburg, Extension Entomology Specialist, A.H. Bruneau, Extension Crop Science Specialist, W.M. Lewis, Crop Science Extension Specialist, L.T. Lucas, Plant Pathology Extension Specialist, C. Peacock, Crop Science Turf Research, M.A. Powell, Horticulture Extension Specialist, R. Sneed, Extension Agricultural Engineering Specialist, R. White, Crop Science Turf Research

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PROBLEMS ASSOCIATED WITH WARM SEASON GRASSES

Bermudagrass

In contrast to hybrid bermudagrass (Tifway and Tifgreen), common bermudagrass (wiregrass) can be seeded and maintained at a higher mowing height. Common bermudagrass produces a more open , weed prone lawn, has a wider leaf, is less cold tolerant, and exhibits more seedheads but requires less maintenance. Tifway (T-419) and Tifway II are the best all-purpose hybrids for use in lawns, but they may require more frequent mowing and more fertilization than common bermudagrass. Both grasses are finer in leaf texture, are denser, and exhibit fewer seedheads than common bermudagrass, and they are pollen free. Midiron and Vamont are very aggressive, coarse-leafed, cold-tolerant cultivars that must be vegetatively planted.

Tifgreen (T-328), Tifgreen II, and Tifdward require very intensive management and are not usually recommended for residential use. Tifway (T419) is tolerant to sod webworm and mole crickets. Tiflawn (T57)is somewhat resistant to nematode injury. Tifgreen (T328) has good resistance to Helminthosporium sp. but is susceptible to armyworm, sod webworm, and scale insects. Tifdwarf is very susceptible to smog injury and sod webworm.

Guymon is a new, seeded, very coarse, cold-tolerant cultivar, similar to common bermudagrass in appearance. Little published information is available on the newest cultivar, Sahara.

Midway is susceptible to hunting billbug

Because of their aggressive nature, Bermudagrasses have very few serious pest problems but are subject to sting nematode damage when grown in sandy soils. Nematode damage leads to shallow- rooted plants that do not respond to water and fertilizer, resulting in thin, weak areas invaded by weeds. If nematodes are suspected, submit a soil sample for analysis.

Diseases

Spring dead spot is a serious disease of bermudagrass. Symptoms of this disease are small circular dead spots 6 inches to 2 feet in diameter in the spring as bermudagrass resumes growth from winter dormancy. This disease usually develops in 4-to-6-year old bermudagrass that has been managed at a high level. Bermudagrass grows over the spots slowly, or weeds invade the affected spots, during the summer. The spots may occur in the same place and enlarge for 2 or 3 years and then disappear. Factors associated with development of this disease are high rates of nitrogen fertilizer and accumulation of excess thatch. Management practices that use lower rates of nitrogen and thatch removal will help prevent spring dead spot.

Nematodes. Several nematodes including sting, ring, stunt, lance, stubby-root, and spiral nematodes are commonly found in soil from bermudagrass turf. Serious damage to bermudagrass has been associated with the sting nematode. The symptoms of damage by the sting nematode are poor turf that does not respond quickly to nitrogen fertilizer and wilts quickly during dry weather. The roots are stunted and very shallow. Although nematicides will control the sting nematode, they are very toxic and must be applied by licensed applicators. A good management program that includes fertilizer and irrigation to prevent drought stress will help bermudagrass overcome the effect of these nematodes.

Dollar spot , caused by the fungus Sclerotinia homoeocarpa, is sometimes a problem on bermudagrass turf in late summer. Symptoms of this disease are small brown spots 1 to 3 inches in diameter. The spots may become so numerous that the turf has a general brown appearance. The disease usually develops on bermudagrass turf that has not been fertilized adequately with nitrogen. The use of good management practices, including proper amounts of nitrogen and water, will help bermudagrass overcome this disease.

Other diseases seen on bermudagrass are brown patch , caused by species of the fungus Rhizoctonia, and leaf spot , caused by species of the fungus Helminthosporium.

Centipedegrass is not very drought tolerant and may be damaged during very dry weather. Irrigating when needed will help reduce damage from drought stress. Localized dry spots of soil that are hydrophobic (difficult to wet) have been associated with declining patches of centipedegrass. The soil in these patches may be powder-dry even after rain or irrigation. Loosening of the soil and heavy irrigation is needed to wet the soil in these spots.

Centipedegrass will usually spread over dead areas more rapidly if the old grass is removed and the soil loosened. New sprigs should be planted in the areas in late spring or early summer for faster recovery.

Centipedegrass is not very shade-tolerant and does not grow well under trees with dense foliage. Root competition from nearby trees may increase drought stress and sometimes causes fairy ring-like symptoms. The landscape should be redesigned to use mulch or shade-tolerant plants in these areas if the trees cannot be removed.

Herbicide Injury

The use of certain herbicides (as sprays or in fertilizers) has been associated with the decline problem. Centipedegrass is very sensitive to some herbicides and recommended herbicides should be used according to label directions for centipedegrass. Damage has been observed where fertilizers containing some types of herbicides have been applied at rates suggested for other types of turfgrasses. In addition to herbicide damage, too much nitrogen is often applied from the herbicide plus fertilizer products for centipedegrass and causes problems discussed above. Once a good stand of centipedegrass is established, weeds usually are not a problem because of the allelopathic activities that centipedegrass has against other plants. Therefore, herbicides should not be needed each year on centipedegrass if it is managed properly.

Disease

Centipede decline is a name used to describe the most common problem observed on centipedegrass. Recent research in North Carolina has shown that this problem can be caused by several different factors.

Nutritional factors, including low potassium levels in sandy soils, high phosphorus levels, and the use of too much nitrogen fertilizer have been associated with this problem. Excess nitrogen increases the thatch and reduces cold and drought tolerance of centipedegrass. Usually not more than 1 pound of nitrogen per 1000 sq. ft. per year is needed on sandy soils. The use of fertilizers that are high in potassium and low in nitrogen may help to reduce stress during the summer and winter. This grass has grown well on clay soils without any fertilization for many years.

Low or high soil pH has also been associated with the problem. High soil pH will cause centipedegrass to turn bright yellow, especially in the spring, due to iron deficiency (iron chlorosis). A pH of 5.5 is best for centipedegrass.

High phosphorus levels can increase iron chlorosis since it can replace iron in the plant. The use of fertilizers high in phosphorus may contribute to the decline of centipedegrass. Soil test results should be used to correct these problems and to determine fertilizer requirements.

Fairy rings have also been shown to cause some centipede decline problems.

Improper mowing and fertilization have been implicated as factors in experimental plots where centipede decline developed. More decline was observed in the spring where the grass was mowed at 2 inches than at 1 inch and where high nitrogen rates (2 pounds per 1,000 sq. ft.) were used. More thatch accumulated at the higher mowing height with high nitrogen and caused the stolons to be above the soil. These stolons are more susceptible to damage by cold weather. More centipede decline usually occurs in the spring and summer following very cold winters or following winters with unusually warm weather and then late cold periods.

Nematodes have been associated with the decline in sandy soils in some cases. The sting nematode has been shown to cause very serious damage on centipedegrass in sandy soils in southeastern North Carolina. Centipedegrass affected by this nematode will become thin and even die during hot-dry weather.

The importance of the ring nematode which occurs frequently in centipedegrass lawns is not known. Damage from large numbers of this nematode has not been observed in many test plots established in the state. Since no nematicides are currently labeled for use in residential lawns, management practices will have to be used to help overcome damage from nematodes.

A good management program that includes irrigation when needed can be used to overcome the effect of the ring nematode, but not the sting nematode. Another grass such as bermudagrass or bahiagrass may be an alternative for use in lawns with high levels of sting nematodes. Incorporation of organic matter in the soil may help overcome nematode damage; however, care must be taken to avoid too much nitrogen being released for centipedegrass.

Dollar spot is a disease that is often seen on centipedegrass during the summer. The symptoms of this disease are light brown spots 2 to 4 inches in diameter. It does not appear to cause serious damage. Centipedegrass that is declining because of other factors may have more dollar spot than nearby healthy grass.

Brown patch has been identified on centipedegrass during wet weather in the spring, summer and fall. The symptoms in cool, wet weather are usually large circular patches of thin grass. Early symptoms may be circular yellow patches. The grass may continue to decline in the affected patches, especially in dry weather, for a long time after the disease has stopped activity. Some fungicides may help control these diseases, but usually are not needed.

Zoysiagrass is well adapted to the piedmont and coastal plain and is usually vegetatively planted, although procedures are now available for seeding common zoysiagrass.

Once zoysiagrass is established, it can become thatchy or fluffy looking due to an accumulation of dead, decaying plant residue at the soil surface. This is most likely when mowed high and infrequently or when heavily fertilized. Thatch needs to be removed every two to three years, but care should be taken because the recovery rate of zoysiagrass is slow.

Zoysiagrasses perform best when mowed with reel mowers, however, good performance can be achieved using a rotary mower with sharp blades set as low as possible without scalping. Uneven terrain may prevent zoysiagrass from being mowed as short as desired.

Emerald zoysiagrass has very fine leaves, good winter hardiness, shade tolerance, and wear resistance, a moderate rate of spread, and a dark green color. Meyer zoysiagrass has a medium leaf texture, is less shade tolerant, and lighter in color than Emerald. Meyer establishes more quickly than other zoysiagrasses and is the most cold tolerant. Zoysia matrella is intermediate in leaf texture, density, cold tolerance, and low-temperature color retention compared to Emerald and Meyer. Emerald is susceptible to Dollar Spot.

Meyer is susceptible to hunting billbug and nematodes. Rust is also reported on zoysiagrass.

Brown patch

Gray Leaf Spot

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