By Brian Aynardi, Ph.D.
Northeast Research Scientist
A problematic and perennial problem of all types of managed turf, fairy ring is caused by a plethora of basidiomycete fungi. The rings grow in circles because fungi grow and expand radially. It’s an especially unwanted blemish on high-profile areas on golf courses such as fairways, approaches, and greens.
Fairy Ring Symptoms
Fairy ring doesn’t infect the host plants that exhibit symptoms. Rather, symptoms are by-products of the degradation of organic matter in the turf profile. This is an important concept to consider from a fungicide application strategy, because the fungicide must get to where the pathogen resides. Significant post-application irrigation immediately following fungicide treatment is imperative, as is the incorporation of a wetting agent where applicable.
There are three types of fairy ring of turfgrass with the following symptoms:
TYPE I
Hydrophobic soil conditions result in the death of turf in rings or crescent shapes
TYPE II
A green ring or semi-circle of accelerated growth that may or may not be accompanied by mushrooms
TYPE III
A ring or semi-circle of mushrooms
Due to the loss of turf, Type I fairy ring should be considered the most problematic, whereas Type II and Type III are cosmetically unsightly.
How to Control Fairy Ring
From a fungicide control perspective, it is important to understand where fairy rings exist at your facility. Since the rings increase over time, knowing where fairy ring occurs and mapping these locations is a great idea. It is also critical to make preventive applications where fairy ring is problematic.
The pathogens become active when soil temperatures rise into the mid-50s, and a good rule of thumb for timing an initial preventive application is when the soil temperature at 2” depth is 55°F. The pillar in fairy ring control for the last few decades has been flutolanil, which is a succinate dehydrogenase inhibitor (SDHI) fungicide specific to basidiomycetes. The formulation of this mainstay has been upgraded to a suspension concentrate: Pedigree Fungicide SC, the first liquid formulation of flutolanil.
What is flutolanil?
Flutolanil is the active ingredient in Pedigree. Unlike competitive products with the same active ingredient, Pedigree is a liquid, suspension concentrate formulation, which can be easier to handle and apply, compared to watered-dispersible granule (WG) formulations. Flutolanil is a SDHI fungicide (FRAC 7) used for disease control in turf. Applied to the soil or the base of the plant, flutolanil moves upward efficiently in the plants through acropetal translocation. Flutolanil has no documented cases of resistance, making it ideal for a rotation programs.
The proven track record of flutolanil makes it a necessity in a preventive fairy ring program, and applications of Pedigree with your wetting agent of choice are strongly recommended. Although there is a low risk for development of fungicide resistance with the pathogens causing the disease, rotation of different modes of action is important. Fungicides from the DMI and QoI (strobilurin) groups have also demonstrated excellent control, and the polyoxins may also aid in control. Incorporating these groups with Pedigree is a strong preventive programmatic approach to controlling fairy ring.
The largest fairy ring is almost a half-mile in diameter: as incredible as that sounds, you don’t want it on your turf. Monitor your soil temps and use a rotation program featuring Pedigree to stop the rings before they start. And if you want to hear some great folklore about fairy rings, Dr. Mike Fidanza of Penn State University has a million of them!