FAIRY RINGS ON GOLF COURSES – IDENTIFICATION AND MANAGEMENT
Leon T. Lucas, Ph. D.
Carolinas Golf Association Agronomist
Fairy rings have become a severe problem on golf greens in recent years, especially on high sand-content greens. The disease has developed on many new greens and on some older greens where fairy rings were not observed in previous year. Fairy rings that were present in years past without much damage caused serious damage during very hot and dry weather in 1998. Fairy rings have been difficult to manage on many courses.
Symptoms of fairy rings on bentgrass greens have ranged from small green patches, small green rings, yellow depressed rings, dead patches in hot weather and to large dead rings. Mushrooms are not usually present in the rings. In some cases the small green patches and rings have been incorrectly diagnosed as take all patch on bentgrass. Many of the rings will continue to enlarge over the years and some will grow together and result in large irregular rings. The rings continue to enlarge for several to many years, or in some cases may suddenly disappear. Some develop into half-circle rings because the fungus does not continue to grow in part of the ring. The soil in the patches, or in the rings, usually is dry and hydrophobic when the symptoms are the most severe during the summer. The soil from the active ring has a "mushroom smell" and the thatch will usually be a lighter tan in color compared to the thatch layer a few inches away. The older classification of different types of fairy rings is questionable for the ones that occur on golf greens. Some fairy rings have been observed to have green rings in the spring and change to dead rings during the summer. Mushrooms may develop in the rings later in the summer or once every 2 or 3 years depending on the weather conditions.
The damage from fairy rings has been observed to be more severe on high-sand-content greens. The dry and hydrophobic soil that often develops in the rings appears to cause the most damage. The hydrophobic soil can be diagnosed by placing a drop of water on the soil or thatch. The drop of water will remain on the hydrophobic surface and often will evaporate before wetting the soil. Mycelium of the fungi that causes the fairy ring will usually grow on the thatch layer if a plug of the turf from the ring is placed in a moist chamber for a few days. The greener grass in the rings probably is caused by the release of nitrogen from the decomposition of organic matter in the thatch and soil. Some of the fungi may release toxic materials to turfgrasses such a hydrogen cyanide. Some of the fungi may be pathogens on the turfgrasses as has been shown for Marasimus blight on American beachgrass.
Mushrooms or puffballs of the different genera of fungi that cause fairy rings usually are not present on the greens. A small white puffball, a Lycoperdon species, that turns brown and firm with age is an exception and may be present in fairy rings on golf greens. Fungi that cause the fairy rings are common inhabitants of wooded areas and the fungal spores probably blow onto the golf greens or were in the soil when the golf course was constructed. The thatch layer on golf greens provides an adequate source of organic matter needed for these fungi to grow.
Management of fairy rings should be considered even during construction. Large sources of organic matter, such as tree stumps, should be removed from the turf area. Some types of organic matter, such as sawdust, incorporated into soil mixes have been associated with more fairy ring problems. Sterilizing soil may increase fairy rings on new golf greens because many of the antagonistic microorganisms to the fairy ring fungi are killed. The lower level of microbial activity in high sand mixtures may explain why fairy rings are usually more damaging on these types of greens. Also, some of the new fungicides that are labeled to control fairy rings may even increase some types of fairy ring problems because many of the antagonistic fungi may be killed. Removal of the soil in the fairy ring affected area has been recommended for large fairy in lawns. This practice is usually not practical on golf courses. Rototilling the soil in the ring and one foot to the outside and the inside of the ring and replanting the turfgrass has eliminated the fairy rings in many cases. The rototilling apparently disrupts the fungus in the soil and allows the grass to grow.
Localized dry spots of soil on many golf greens may be caused by fairy ring fungi. Many of these spots have been observed to develop into typical fairy rings one or two years later. Some unusual symptoms for fairy rings and localized dry spots are green patches of grass surrounded by large areas of hydrophobic soil.
Management practices that are used for localized dry spots to prevent the soil from becoming dry and hydrophobic in the rings will help to reduce the damage from fairy rings. Aerification and watering of rings to wet the soil is effective in some cases. Frequent use of wetting agents helps to reduce the damage from hydrophobic soil in fairy rings in most cases during the summer. The fungicides, Prostar and Heritage, are labeled for the control of fairy rings and have controlled some fairy rings and localized dry spot problems. These fungicides have not controlled fairy rings in all cases. The fungicides may not control all types of fungi than can cause fairy rings and the materials may not penetrate deep enough into the soil where most of the fungus is located. In some cases the fairy ring symptoms disappeared soon after treatment with the fungicides, but appeared again the next year. The green effect of fairy rings can be masked sometimes by applying extra nitrogen at times of the year most favorable for the grow of the grasses. Extra fertilization is not usually practical on bentgrass golf greens during the summer because it would encourage the development of other diseases such as brown patch.
Fairy rings have been observed for hundreds of years in turf with many different effects on turfgrasses. Relatively few studies have been done on this disease on turfgrasses with most of the information in recent years being observations. These are difficult diseases to study and manage because the disease development can be variable from year to year.
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