Fairy ring
Author: Lee Miller, University of Missouri
Reviewed by:Name, Organization
Pathogen
Over sixty different basidiomycete species such as Marasmius oreades, Lepista nuda, Coprinus spp., Bovista dermoxantha, and Vascellum curtisii, have been reported causing fairy ring in turfgrasses. Some of these species include. Fairy ring symptoms have been the subject of folklore since the Middle Ages, being linked to superstitions of cause such as “fairies danced the previous night” or “the burnt ring from a sleeping dragon’s tail”.[1] In reality, fairy ring symptoms are caused by a subsurface fungal colony where the density of mycelium is greatest.
Symptoms and Signs
Fairy ring symptomology occurs as sometimes large (> 3 m diameter) rings or arcs in several different forms. Shantz an Piemesel (1917)[2] categorized these types as (I) fairy rings that cause severe turfgrass loss, (II) fairy rings that only exhibit stimulated turfgrass growth and (III) rings of basidiocarps (mushrooms or puffballs). One, two, or all three of these symptom types may occur at the same time. Type II, green rings are caused by the release of plant available nitrogen in the form of ammonia by the fairy ring fungus while it degrades soil organic matter. Type I ring necrosis may be caused by a number of factors, but most often is the result of the underlying soil being rendered hydrophobic by the abundant mycelial mat or organic acid byproducts. Fairy rings may also be categorized based on the depth of the mycelium within the profile, either edaphic (deeper soil dwelling species), lectophilic (thatch and upper 5 cm of soil profile) or superficial (only in the upper thatch layer). Unless molecular methods are utilized, fairy ring fungi are speciated based on the basidiocarp and basidiospore characters.
Ecology and Spread
There is some conflict in the literature on whether the primary source of fairy ring inoculum is a bit of fungal mycelium or a single basidiospore. Basidiospores would be spread via wind or water, and both sources could be spread via animal or mechanical movement. From the initial point of growth, fairy rings grow radially outward in soil and thatch. Several fairy rings may form in a single area, and when they collide unilateral or bilateral extinction may occurs. This phenomenon may cause stand symptoms to appear scalloped or in arcs.[3]
Geographic Distribution
Fairy rings are have been documented worldwide wherever turfgrass is grown.[4]
Management
Fairy ring management depends on the symptom type and level of damage. In the case of Type II or III fairy ring symptoms, management may involve simply masking the green rings with iron or nitrogen applications, or basidiocarp removal. Particularly on high amenity turfgrasses, Type I fairy rings can be particularly troublesome and require more intensive cultural or chemical control methods.
Cultural Control
Control of an Type I fairy ring problem is difficult because it normally requires both the remediation of soil physical properties (i.e. water infiltration) and curative control of the fungus. Aerification, and thorough soil wetting through the use of soil surfactants, heavy irrigation, and water injection are recommended cultural practices to aid in water penetration and turfgrass recovery. More labor-intensive methods requiring turfgrass re-establishment such as soil replacement or soil fumigation have also been previously suggested. In some cases, mixing of infested and non-infested soils to promote microbial antagonism has been effective at reducing symptoms.[5] Prevention of fairy ring focuses on thatch management via aerification, verticutting and topdressing by attempting to balance the rate of thatch production with degradation.[6]
Chemical Control
Certain fungicides in the quinone oxidase inhibitor class, or flutolanil are most often recommended for curative fairy ring control. If hydrophobicity is present in the infested soil profile, fungicide applications should be tank-mixed with a soil surfactant and watered-in to insure delivery to the target rootzone. A preventive strategy utilizing spring applications of demethylation-inhibiting fungicides has also been recently developed for fairy ring control on golf putting greens.[7]
Host Resistance
Due to the etiology of the disease (little or no infection of living plant material), resistant turfgrass species or cultivars are unknown and breeding for resistance may not be plausible.
Diagnostic procedures
Fairy ring is most often diagnosed based on the green ring symptomology in the field or basidiocarp production. An additional diagnostic character can be the smell of the infested soil and thatch layer, which may smell of mushrooms or a “musty, old tent”. Fairy ring incidence is rarely diagnosed to the particular species, or even genus level, due to the ephemeral nature of the basidiocarp and cost of molecular diagnostic procedures.
Cited References
- ↑ Ramsbottom J. 1953. Mushrooms and Toadstools. Collins, New Naturalist Series: 306.
- ↑ Shantz H.L., and Piemesel R.L., 1917. Fungus fairy rings in eastern Colorado and their effect on vegetation. Journal of Agricultural Research 11: 191-245.
- ↑ Smith JD, Jackson N, Woolhouse AR. 1989. Fungal Diseases of Amenity Turfgrasses. London: E & F.N. Spon Ltd.
- ↑ Beard, J.B., & Tani, T. (1997). Color atlas of turfgrass diseases. Tokyo, 107 Japan: Soft Science, Inc.
- ↑ Couch, H.B. (1995). Diseases of turfgrass. Malabar, FL: Krieger Publishing Company.
- ↑ Smiley, R.W., Dernoeden P.H., & Clarke, B.B. (2005). Compendium of Turfgrass Diseases. St. Paul, MN: The American Phytopathological Society.
- ↑ Miller G.L., Soika M.D., and Tredway L.P. 2012. Evaluation of preventive fungicide applications for fairy ring control in golf putting greens and in vitro sensitivity of fairy ring species to fungicides. Plant Disease 96: 1001-1007.
