Chemical control of fairy ring by application with osmotic agent, Osmac

—Examinations for the fairy ring caused by Lepista sordida occurring on Shodoshima Country Club—

Abstract

It has generally been considered that fairy rings occurring on turf are hardly possible to control with fungicides, because the causal pathogens survive in the depths of soil and produce a dense hydrophobic mass of mycelia. These characteristic properties of the pathogens make difficulties to arrive the fungicides toward the pathogens. With such respects, application of fungicide with osmotic agent which is capable of carrying the fungicide to make direct contact with the pathogen was examined in the present study. The fungicide and osmotic agent used in the experiments were daconil (Takeda Chemical Industry Ltd.) and Osmac (Hayashi Chemical Industry Co. Ltd.), respectively. The fairy ring caused by Lepista sordida was selected on zoysia patting green in Shodoshima Country Club, Kagawa Prefecture, Japan.
Treatment of the fairy ring with 10 liter/m² of daconil (1/250 dilution) and a mixture of daconil and osmac (both 1/250 dilution in final) for three times at a 3 week-interval, starting from May 19, 1980, largely reduced the disease symptom in the early of July. No survival of the pathogen was found in soil treated with daconil and daconil-osmac mixture. In August, however, survival of the pathogen was detected in soil treated with daconil alone, while no pathogen was still detected in soil treated with the mixture.
In the next spring, 1981, the fairy ring symptom appeared on the turf treated with daconil alone and untreated control turf.
However, neither symptom nor survival of the pathogen was observed on the turf treated with the dacnil-osmac mixture.
The results presented in this paper strongly suggest that the fairy rings may be controlled with fungicides by the application with proper osmotic agents.