By Richard Rees, Ph.D.
What does it look like?
Initial symptoms of fairy ring are characterized by small rings of lush, exceedingly green grass in turf. As the fungi rings grow, three kinds of fairy ring may form: Type one has a ring of stimulated grass growth surrounded by a ring of mushrooms. Type two has only a ring of mushrooms enclosing seemingly normal grass growth. The third has only a ring of stimulated grass growth. Occasionally, a patch of declining grass growth, or even dead grass, may appear within the ring of stimulated grass.
Host material and range
This troublesome fungus is found in both cool- and warm-season turfgrass throughout the United States. University research reveals that fairy ring tends to be a problem on newly constructed greens and turf not maintained by regular core aerification. Jack Fry, a professor in Kansas State University’s Department of Horticulture, Forestry and Recreation Resources, said, “Anything that encourages an accumulation of organic matter on the green — whether it’s a buildup of thatch due to a lack of aerification or the peat moss used to construct a new green — provides a good habitat for fairy ring.”
Poorly maintained, thatched or drought-stressed turf on sandy soil is most susceptible to fairy ring damage. After initial symptoms appear in spring and summer months, the underground fungal mat increases rapidly, up to 16.5 feet per year. The fungal mat makes the soil impervious and often causes unsightly patches of malnourished, or even dead, grass.
When the fairy ring fungus is ready to reproduce, mushrooms appear around the fungal mat’s rim. These mushrooms release spores through the gills under their cap, which sends the fungus into the air. One mushroom can produce millions of spores.
Sound agronomic practices, such as adequate watering and properly timed nitrogen fertilization, can help reduce the severity of fairy ring. Avoid excessive watering and fertilization of turf, as this may stimulate or worsen the fungus. To maximize the effect of nitrogen application, apply a nitrogen fertilizer prior to the appearance of fairy ring. Curative applications require high rates and are generally not as effective as properly timed preventive applications.
When battling fairy ring, the ideal regimen combines a preventive treatment followed by a curative application, if necessary.
For effective control of fairy ring, apply a preventive fungicide that will eliminate fairy ring and keep out other diseases. Because fairy ring tends to make soil hydrophobic, try tank mixing the fungicide with a wetting agent at the rate of 4 ounces/1,000 square feet to make sure it penetrates the soil. Follow with a second application about two weeks later.
As a curative, spray surfaces with a fungicide to eliminate fair ring’s dark, ugly circles.
What can you do?
Cultural practices to limit fairy ring damage include the following:
* Digging an area one foot beyond the ring and removing all sod from the area. Then remove all soil in that area to one foot. Don’t spill any on the lawn. Refill hole with new soil and reseed/re-sod area.
* Punching holes at least every foot in yellow and dying areas. Pump large amounts of water in to the ground to depth of 10 to 24 inches.
* Removing lawn clippings after mowing to reduce spreading.
* Applying moderate rates of nitrogen fertilizers.
Richard Rees, Ph.D., is fungicide technical development manager for Bayer Environmental Science, where he is responsible for coordinating all fungicide technical development activities. Rees holds bachelor’s degrees in physiology, biochemistry and genetics from Nottingham University, England. He received his doctorate in life sciences from The Trent University, also in Nottingham, specializing in the mechanisms of action of xenobiotics in isolated plant cells.
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