Turf - Research on the Control of Fairy Rings

Fairy rings in turf are caused by several fungi. To date, control has been very limited. However, new research offers some promise. The following is an article on the subject from the University of Kentucky.

Certain soilborne fungi produce "fairy rings" in turfgrasses. These fungi grow in the soil, feeding off of dead organic matter in the soil and producing rings or arcs of symptomatic turf and/or mushrooms. The symptoms produced are of three general types:

Type I: Rings or arcs of necrotic (dead) turf; localized dry spot (hydrophobic soil or thatch) is often associated with these.
Type II: Rings or arcs of stimulated turf growth; localized dry spot may be associated with these.
Type III: Rings or arcs of mushrooms only.

For fairy rings in lawns and landscapes, my recommendation is to rely on cultural practices to reduce symptoms. Such practices include proper fertilization and irrigation, reduction of thatch, the use of soil surfactants, and aerification to improve penetration of water.

For putting greens and croquet courts, where very high standards of playability are held, fungicide applications may play a part in fairy ring management. Labeled fungicides include Endorse, Heritage, Insignia, and Prostar. (Zerotol is also labeled but I am unaware of data showing this product to be effective against fairy ring, and its track record in research against other diseases is so poor that I can't justify including it in the following discussion in the absence of data showing efficacy.)

Recent Research

Recently a team of excellent turfgrass pathologists from several states, led by Dr. Mike Fidanza of The Pennsylvania State University, conducted tests of fungicidal control of fairy ring. They tested the four fungicides listed above at their labeled rates applied with and without the soil surfactant Revolution at 6 fl oz/1000 sq ft. In two of their tests, these treatments were applied in 2 and in 4 gal spray volume/1000 sq ft. All treatments were applied twice at approximately a 4-week interval.

One of the findings from their study was that each of the fungicides sometimes failed to provide any suppression of fairy ring symptoms when the product was applied alone in a volume of 2 gal/1000 sq ft. We had a similar result in a test using Prostar several years ago.

However, the results of the trial were not completely gloomy. The researchers found consistently that a tank-mix of each fungicide with Revolution soil surfactant resulted in significantly reduced fairy ring symptoms 4-6 weeks after the second application. They also found that increasing the spray volume from 2 to 4 gal/1000 sq ft typically improved disease control. In a number of instances, the best treatment for a given fungicide was the tank-mix of that fungicide plus Revolution applied in 4 gal/1000 sq ft.

Another interesting element of their studies was how the impact of a curative application of the fungicide-Revolution tank-mix didn't necessarily show up during the same growing season the application was made. In one test, the benefit was not seen during the season of application but it was seen during the following growing season.

Interestingly, testing of Revolution by Dr. Lane Tredway at North Carolina State University suggests that the application of this product alone (no fungicide added) can help to alleviate fairy ring symptoms.

Implications

These studies suggest that, if one is planning to use a fungicide for fairy ring control, which product one chooses is less important than application in combination with an appropriate soil surfactant in sufficient volume. Recognize that numerous fungi can produce fairy rings. Some of these fungi may not be sensitive to labeled fungicides at normal use rates; others may be too deep in the soil to be affected by the fungicide.

Reprinted from "HOW TO GET THE MOST OUT OF A FUNGICIDE SPRAY FOR FAIRY RING" By Paul Vincelli in the July 2, 2007 edition of the Kentucky Pest News from the University of Kentucky, College of Agriculture.