It’s No Fairy Tale… It’s Fairy Ring!
Fairy ring is a problematic disease of sand-based putting greens, especially on ultradwarf bermudagrass (UBD) putting greens. Previous research conducted by Dr. Lee Miller demonstrated preventative fungicide applications, especially with DMIs, greatly limited fairy ring development. However, DMIs are not widely used on UDBs due to the potential for phytotoxicity.
There are three types of fairy ring in turfgrass. Type I and Type II are typically more problematic during extended periods of drought (causing hydrophobic soils) or soils having low fertility (1,2,3,6). Type III (mushrooms only) becomes more of an issue in extended wet periods. For more on fairy ring, follow this link:
Figure 1. Type I fairy ring (3)
Figure 2. Type II fairy ring (4)
Figure 3. Type III fairy ring (5)
There are a few management practices one can do to mitigate the unsightly symptoms and signs of fairy ring. Dr. Miller demonstrated that applications of DMIs or other fungicides when soil temperatures in the spring were between 55 and 70°F inhibited fairy ring development later in the year. Currently, soil temperatures are hovering around 55°F in most areas of North Carolina. It is imperative that turf managers time these applications based on soil temperatures rather than air temperatures. For example, some superintendents made the decision to apply fungicides during the warm spell in February—this will likely result in more applications for fairy ring. Unfortunately, mother nature threw us a curve ball. Yet, based on current soil temperatures and the long-term forecast, preventative fairy ring applications are warranted in the next few weeks. It is important to remember that Dr. Miller showed preventative control at a range of temperatures, which means you still have plenty of time to get these applications on the ground.
When applying fungicides targeted at fairy ring and other soil-borne pathogens it is crucial to optimize control of the disease through the following techniques (2,3,6,8):
- Post-Application Irrigation and High Carrier Volumes:
- Post-application irrigation has been proven to increase efficacy of fungicides targeted at soil-borne pathogens, particularly fairy ring. Post-application irrigation pushes the fungicide downward in the soil profile allowing for more active ingredient to contact the pathogen. Applying 0.25 inches of irrigation after fungicide application provides good soil-borne disease control.
- Spraying fungicides at higher carrier volumes (≥ 4 gal/1,000 sq. ft.) have a similar effect to post-application irrigation on fungicide distribution. Therefore, this application practice provides another option for fairy ring control.
- Soil Surfactants:
- Applying soil surfactants regularly can alleviate the symptoms of fairy ring in a number of ways. For Type I, soil surfactants reduce the hydrophobicity in the soil preventing localized dry spot. Soil surfactants also ease Type III symptoms/signs by pushing water through the soil profile providing better drainage to poor draining soils—where Type III commonly occurs. Lastly, soil surfactants advance fungicides further into the soil profile allowing for more fungicide to contact the pathogen. Figure 4. and Figure 5. exhibit the positive effect of soil surfactants on both water and fungicide distribution in a bare 90% sand/10% peat moss USGA putting green soil mix.
Figures 4 & 5. Soil columns were treated 3 times (once every 2 weeks) with one of three soil surfactants prior to fungicide application. Leachate (i.e. drainage) from the columns was collected every other day. Figure 4. demonstrates that soil surfactants advanced water downward in the soil more than the control. This is exhibited through the greatly increased leachate amounts. Figure 5. shows increased downward movement of the fungicide myclobutanil in soil treated with soil surfactants.
The moral of this fairy tale is to time fungicide applications correctly and optimize them by including soil surfactants in your spray program. This will help with both fairy ring control and management of other soil-borne diseases. The reduction in soil hydrophobicity, as well as the advancement of fungicides further down the soil column to lower parts of the turfgrass plant, provide greater turf quality and disease control when targeting fairy ring.
Finally, based on our recent findings, there are some other best management practices turf managers can implement when targeting turfgrass diseases such as not mowing and removing clippings for 1-2 days after a fungicide application. Not mowing the day after application has been found to greatly decrease the amount of fungicide removed from the turfgrass stand (7). Stay tuned for more on that…
This article was written by Wendell Hutchens. Wendell is a Master’s student in Jim Kerns’ lab.
- Penn State Extension: Fairy Ring
- Kennelly, Megan. Fairy Rings in Turfgrass. Kansas State Agricultural Experiment Station and Cooperative Extension Service. EP-155. December 2008.
- Butler, E.L. Fairy Ring in Turf. North Carolina State University Turffiles. November 10, 2017.
- Luxury Lawns: Fairy Rings
- Green Industry Pros: Fairy Ring Fungus Flourishes in the Summer Months Due to Heavy Rain
- Fidanza, Mike; Wong, Frank; Martin, Bruce; McDonald, Steve. Treating fairy ring with fungicides, new soil surfactant. GCM: 121-125. May 2007.
- Jeffries, M.D., Gannon, T.W., and Yelverton, F.H. Off-Target Pesticide Displacement and Fate in Turfgrass, Riparian and Aquatic Systems. 2017.
- Benelli, Jesse J., “Improved Fungicidal Control of Large Patch through Optimal Use of Surfactants and Spray Rate Volume.” PhD diss., University of Tennessee, 2016.
- Biology and management of fairy rings on golf putting greens Miller, Gerald Leo, Jr. North Carolina State University, ProQuest Dissertations Publishing, 2010. 3429673.