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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 COOL SEASON GRASSES

Bentgrass

Managing High-sand-content Greens

Good quality bentgrass can be grown on many high-sand-content golf greens if proper construction and management techniques are used. Great care should be taken during the construction process to ensure that proper sand and peat types are used and mixed uniformly. Mixing can be done best offsite prior to moving the mixture to a green with very carefully prepared subsurface contours. The mixture must have a uniform depth, 12 to 14 inches, over the green for proper results.

Use of sands that have correct particle sizes and mixed properly with the organic matter to give desired percolation rates in the 10-to-15-inch per hour range is the first step in preventing many of the problems associated with these greens. This can be done only by using physical soil analysis which is available from several different laboratories. Samples should be taken from the sand at time of delivery and analyzed to be sure that all of the sand meets specifications. Special attention should be given to the selection of topdressing mixtures to avoid layers of different types of soils. The same mixture used in greens construction would be best if the greens are performing well. Mixtures different from the original mixture should be used only following aerification so that it will mix with the top 3 to 4 inches of existing material. The type of peat or organic matter used in the mixture will make a big difference in soil properties. For example, a sand mixed with a sphagnum peat resulted with a mixture that had a percolation rate of 17 inches per hour. The same sand mixed with a reed-sedge peat resulted in a mixture with a percolation rate of 5 inches per hour. The addition of some loamy soil, especially with sphagnum peat, to increase cation exchange capacity has worked well in some cases. Addition of some sandy loam soil resulted in greens that were easier to manage, however, follow physical analysis recommendations for any materials used. The USGA recommendations for golf green construction are the best guidelines to follow for drainage, subsurface contouring, and the addition of the top 12 to 14 inches of sand mixture. Also, greens with high-sand-content may need a totally different management program than that used on old greens or on greens with different mixtures. These high-sand-content greens usually become easier to manage after several years of growth.

Environmental conditions surrounding bentgrass greens are important for all types of construction, but are very important for the high-sand-content greens. Summer decline usually appears first on greens in low areas that are surrounded by trees on the east, south and west sides. Wind movement is usually restricted in these areas and results in hotter and more humid environments than on nearby open greens. Trees and undergrowth should be removed on the southwest side to improve air movement from predominant southwest winds during the summer. The surface temperature of greens with restricted air flow is usually higher than nearby open greens. Deep root systems usually develop in the sand mixtures during the fall and spring but decline severely during the summer. The first above- ground symptom associated with the root decline is yellowing of the grass. The turf continues to decline and becomes weak and thin and may die in late summer. This condition is often referred to as black layer or Pythium root rot, however, the name summer decline seems more appropriate since a number of factors have been associated with the problem.

A black layer may develop near the surface, or deeper in the soil, and has been indicated as the cause of the decline in some states. The black layer appears to be a symptom of the problem because anaerobic (lack of oxygen) conditions in the soil are needed for it to develop. The black layer is visible in the high-sand-content greens due to the light color of the sand. It is formed from the reduction of sulfur compounds in low oxygen conditions to sulfides that combine with iron and manganese which are black. Sulfur is oxidized to sulfates which are not black in soils with good aeration. The first indication that this layer is developing is a bad smell, like rotten eggs, from sulfides in the soil. The lack of oxygen (drowning) can kill the bentgrass roots and the sulfides can be toxic to roots. Therefore, the roots probably die sometime before the black layer becomes visible in the soil. Also, algae have been indicated as the cause of the black layer, and are associated with the problem in many cases. The growth of algae is favored by wet soils which produce substances that interfere with the movement of water in sandy mixtures. The algae contribute to the development of anaerobic conditions. The best management practices to avoid anaerobic conditions, black layer and algae problems are to irrigate carefully and to aerify the greens as often as needed. The mancozeb fungicides can be used to help control some diseases and algae in combination with the management practices.

Thatch

The development of a thatch layer on the surface of high-sand-content greens contributes to the decline. The thatch layer which has a finer texture than the sand below causes a perched water table and water does not move into the sandy mixture until the layer becomes saturated. Water can be squeezed out of the thatch layer in a plug from these greens for several days after irrigation although the sand mixture below is relatively dry. This saturated condition in the thatch layer causes an anaerobic condition, favors the growth of algae and provides an environment favorable for fungi that cause brown patch and Pythium root rot. A layer of thatch is necessary on these greens to obtain acceptable ball holding qualities. However, mixing of a proper topdressing soil with the thatch is needed to reduce the adverse effects of the thatch layer. Applications of topdressing soil in combination with aerification in the spring and fall has worked best. Aerification with small hollow tines or solid tines has helped to reduce the problem of saturated thatch layers during the summer. Reseeding with bentgrass following aerification in the summer has aided in recovery in some cases. Topdressing with large amounts of sand should be avoided in the summer since abrasive damage from traffic and equipment can cause more damage when the bentgrass is weak.

Dry Spots

Localized dry spots are often a severe problem on high-sand-content golf greens. Dry spots of soil are thought to be caused by sand particles becoming coated with microbical products. Once the soil in these spots becomes dry, it is almost impossible to wet again without aerification or using wetting agents. Stress from dry wilt and extra water needed to wet these areas make bentgrass more susceptible to diseases such as Pythium root rot. Most superintendents have found that it is best to use wetting agents in a preventative program and to keep sand mixtures moist to avoid severe problems associated with localized dry spots. A dry ring is often a problem at the edge of high-sand-content greens where the greens mixture meets native soil. The native soil draws water away from the sand resulting in a dry area. The sand mixture should extend out far enough off the green to have the fairway grass growing on the sand mixture or a barrier should be used between the sand mixture and the native soil to solve this problem.

Nutrient Problems

Nutrient deficiencies and excessive nutrient levels have been identified frequently as problems on high-sand-content greens. Sand mixtures often have very low cation exchange capacities, often less than 2, that cause rapid leaching of nutrients. The low cation exchange capacities and rapid leaching require application of more fertilizer on these greens. Some greens have needed as much as 20 pounds of nitrogen per 1000 square feet during the first year. Small amounts of a complete fertilizer with micronutrients should be applied at frequent intervals to keep nutrients in the root zone.

High soluble salts from too much fertilizer have caused damage on many of these greens due to the low cation exchange capacities and accumulation of salts in the thatch layer. As water evaporates from the turf and soil, the salts may be concentrated around the crowns of the plants. The symptoms of high soluble salt damage are large areas or streaks on a green that turn yellow, begin to decline and even die a few days to several weeks after fertilization. The problem is usually more severe during dry weather when small amounts of irrigation water are being applied. The streaks are usually where the fertilizer application overlapped. Once high soluble salts are detected, which involves a simple extraction procedure and the measurement of electrical conductivity, leaching with large amounts of water from irrigation or rain is the only way to remove them. Smaller amounts of fertilizer should be applied each time to these greens than to ones with higher cation exchange capacities. Even smaller amounts of slow release fertilizers should be used.

Soil Test and Tissue Analysis

Soil test and tissue analysis should be used regularly to determine fertilizer needs of the bentgrass. Soil test results for high-sand-content greens usually indicate a deficiency of phosphorus-, potassium and some micronutrients. The accuracy of recommendations for large quantities of nutrients for low-cation-exchange-capacity mixtures is questionable because tissue analysis from clippings from these greens often show adequate levels of nutrients. Soil test results should be used as a guide to correct any pH problems, nutrient deficiencies or nutrient imbalances by applying small amounts of nutrients at frequent intervals. Application of large amounts of potassium, which is often indicated, could result in damage from high soluble salts if applied all at once. The use of a complete water- soluble fertilizer dissolved in the spray tank and sprayed at rates as low as 1/8 pound of nitrogen per 1000 square feet has worked well on high-sand-content greens. This fertilizer application method is very useful during the summer and has been used all year in some cases.

Diseases

Diseases caused by fungi are often a problem on all types of bentgrass greens. Bentgrass on sand mixtures often appears more succulent and more susceptible to brown patch and Pythium blight. A fertilization program with the lowest levels of nitrogen possible in the summer will help reduce the susceptibility to these diseases. Pythium root and crown rot is very prevalent on high-sand-content greens. Pythium species that cause rot and crown rot have been isolated from up to 90 percent of the plants sampled from these greens. These fungi apparently do not cause significant damage unless plants are weakened by some condition such as anaerobic soil conditions, localized dry spots, high soluble salts or environmental stresses. Correcting or avoiding these conditions will help to prevent damage from this disease in the summer decline complex. A preventive fungicide program is needed during hot and humid weather to help control brown patch and Pythium blight.

Pythium species that cause root and crown rot are different than the species that cause Pythium blight. These fungi, many of which are Pythium graminicola, vary in their sensitivity to fungicides. Consult the current North Carolina Agricultural Chemicals Manual for recommendations. Treatment does not work well once the bentgrass has started to decline. A combination of good management, summer aerification and use of an effective fungicide has given the best results.

Some nematodes have been found in sand mixtures. The damaging nematode most frequently found is the stubby root nematode. This nematode prefers a coarse, wet sand like that used in these greens. It has been difficult to manage this nematode because the currently available nematicide for golf greens does not control the stubby root nematode very well. A good healthy turf is the best means of overcoming damage from this nematode.

Helminthosporium leaf spot caused by Helminthosporium sp. occurs frequently on bluegrass. The leafspot symptoms are small dark spots on the leaves that increase in number and size and cause the leaves to die. Leaf-spots develop in the spring and often continue to develop throughout the summer and fall. The disease will cause a brown color and will reduce the vigor of the turf. Some of the fungi that cause leafspots cause root and crown rots that result in melting-out or fading-out in the summer. Broad spectrum fungicides can be used to control these diseases in the spring before leafspot symptoms become severe. Good management programs that avoid excessive rates of nitrogen and use irrigation infrequently, but enough each time to wet the soil 6 inches deep will help prevent damage from Helminthosporium diseases on bluegrass. Some of the new bluegrass varieties have more resistance to these diseases and should be used.

Red thread is a common disease on bluegrass in the mountains during the summer. This disease is caused by the fungus Corticium fuciforme. The symptoms of the disease are small circular brown areas 6 inches to 1 foot in diameter. The symptoms are very similar to the brown patch that sometimes develops on bluegrass. Red thread can be identified by the presence of a small "red thread" of the fungus that causes the disease at the tip of many of the dead leaves. Small amounts of nitrogen fertilizer can be used to stimulate blue-grass to overcome the disease. Some fungicides can be used to control the disease.

Rust is a serious disease on some bluegrass varieties. This disease is caused by the fungus Puccinia sp. The symptoms of rust are small yellow or brown spots on leaves that enlarge and increase in number until entire leaves are affected. Masses of orange- to rust-colored microscopic spores develop on the lesions. Affected leaves die slowly giving the turf a yellow to brown appearance. The turf will usually become thin and may be more susceptible to other diseases and weed invasion. If a white cloth is rubbed on the affected turf will transfer the rusty colored spores to the cloth. Broad spectrum fungicides can be used, but the best control is the use of improved varieties and good management programs.

Southern blight is a disease that occurs on bluegrass in the mountains of North Carolina. This disease is caused by the fungus Sclerotium rolfsii . The symptoms of this disease are dead circular areas 6 inches to 3 feet in diameter that usually have a tuft of green grass in the center. The disease develops rapidly during hot and wet weather. Even clover and other weeds in the affected spots are usually killed by the fungus. White masses of the fungus and small yellow sclerotia of the fungus are usually present near the soil surface at the advancing edge of the spots. Bluegrass usually spreads back into the spots with good management.

Dollar spot is caused by the fungus Sclerotinia homoeocarpa . This disease sometimes occurs on bluegrass and appears as small circular spots 2 to 4 inches in diameter. A cottony growth may be present in the morning on leaves in affected spots. Good management practices and the use of small amounts of nitrogen will help overcome the effects of this disease.

Brown Patch is caused by the fungus Rhizoctonia sp.

Powdery Mildew is caused by the fungus Erysiphe graminis .

Diseases

Brown patch is the most serious disease of tall fescue. It is caused by fungal pathogen in the genus Rhizoctonia. The early symptoms of this disease are small circular brown patches about 1 foot in diameter that develop during hot wet weather. More patches develop and the older patches may continue to enlarge up to 4 to 6 feet in diameter during hot weather. Lesions that are olive colored in the morning when dew is present, or during rainy weather, develop rapidly on young leaves. As the tissue dries the lesions become very light tan. Lesions may girdle leaves, causing the portion above the lesion to die. Webby mycelium of the fungus may be seen on the lesions and the surrounding grass blades in the morning or during extended periods of humid and cloudy weather in the summer. Vigorously growing plants that have received higher than recommended rates of nitrogen fertilizer during the spring are more susceptible to the disease. Tall fescue established less than one year can be completely killed by this disease. Affected areas may need renovating to correct soil pH and fertility problems and replanting in September or October. Well-established lawns may be damaged during the summer months, but with proper maintenance (proper soil pH, low nitrogen levels in the summer, infrequent irrigation, regular mowing when the grass is dry, and fall fertilization) the grass will usually recover during the fall. Labeled fungicides, applied once every 3 weeks during favorable weather conditions for disease development, will help control brown patch. This treatment is expensive.

Helminthosporium net blotch occurs on tall fescue but usually does not cause severe damage. The symptoms of this disease are dark brown "net" patterns on the leaves. Young seedlings may be killed by the disease, but old plants will usually overcome the damage during favorable growing periods.

Pythium blight can occur on tall fescue during long periods of hot-wet weather. The turf appears to wilt in irregular patches and gray masses of fungus mycelium may be present on the dying grass. Low nitrogen levels, good soil drainage, infrequent irrigation and good air movement will help prevent Pythium blight. Fungicides may be needed to control this disease in highly maintained landscapes.

White patch is a disease that often occurs in one- to two-year old lawns that were planted in recently wooded areas. Symptoms are circular white patches 6 inches to 1 foot in diameter in the summer. Small tan mushrooms (about 1/4 inch in diameter) of the fungus, Melanotus phillipsii usually develop on some of the dead leaves. The tall fescue may become thin in spots, but usually enough plants survive and grow in the fall to fill in the affected spots. Proper soil pH and nutrient levels, especially phosphorus, in new lawns help to prevent or reduce the severity of this disease.

Rust , caused by fungus in the genus Puccinia, occurs on tall fescue and is seen most often in late summer. The symptoms of rust on tall fescue are small yellow spots on leaves with masses of yellow- to rust-colored microscopic spores in the center of the spots. The number of spots may become so numerous that the entire leaf becomes yellow and dies slowly. The turf will recover from rust during favorable growing conditions.

Stripe Smut , caused by the fungus Ustilago striiformis is an occasional problem in tall Fescue.

Abiotic Injuries to Fescue

Drought and heat during the summer can damage tall fescue. Seedlings that are less than one year old may be killed by drought. Old tall fescue plants may go dormant during dry weather in summer and turn yellow or brown. Many of these plants will resume growth during cooler weather when adequate moisture is present. Young tall fescue needs irrigating during hot-dry weather. Older, well established fescue will remain greener with irrigation. In both cases, irrigate infrequently (once every week during dry weather) and apply enough water to wet the soil at least 6 inches deep. A good management program to encourage the development of a healthy root system in the fall and spring will help tall fescue tolerate hot and dry weather.

Diseases discussed under tall fescue and bluegrass such as brown patch, red thread, Helminthosporium diseases, dollar spot, and rust occur on perennial ryegrasses with similar symptoms. Some ryegrass cultivars are very susceptible to rust.

Pythium blight and brown patch are often serious problems on ryegrasses used to overseed bermudagrass in eastern North Carolina. Symptoms of Pythium blight are rapid death of seedlings in circular to oblong areas during warm wet weather. Sometimes gray masses of the fungus may be present in the affected areas giving the condition called cottony blight. Planting ryegrasses in the fall when the weather is cooler will help avoid damage from these diseases. Also, treatment of seeds before or soon after planting with certain fungicides will give good control. Proper watering will help prevent these diseases and improve seedling survival.

Dollar Spot, caused by the fungus Sclerotinia homoeocarpa, Southern Blight, caused by the fungus Sclerotium rolfsii , and Rust , caused by the fungus in the genus Puccinia, are other problems seen in tall fescue.

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