The Influence of Iron Sulfate and Its Elemental Components on Dollar Spot Suppression.

Dollar spot is the most common disease of bentgrass turf and especially devastating on putting greens. The fungus Sclerotinia homoeocarpa degrades the turf by creating silver dollar-sized depressions of dead and bleached turf. In order to prevent this disease, frequent fungicide applications are required throughout the growing season. Cultural management strategies and disease resistant varieties may reduce the severity of disease. Our goal is to explore alternative options for suppression of dollar spot using ferrous sulfate. This research was established to determine if ferrous sulfate and its elemental components are capable of reducing dollar spot epidemics. Research trials were conducted at the Virginia Tech Turfgrass Research Center in Blacksburg, VA in 2012 and 2015. Treatments were applied as follows: control, Hi-Yield FeSO₄ at 48.8 kg ha^-1, Hi-Yield Sulfur at 10.3 kg ha^-1, and Sprint EDTA iron chelate at 11.2 kg iron ha^-1. All treatments were applied bi-weekly as liquids and replicated four times. Dollar spot counts and turf quality were each monitored and recorded throughout the summer. When disease pressure became unacceptable, a fungicide was applied and plots were allowed to recover for a new dollar spot epidemic. Ferrous sulfate improved turf quality and reduced dollar spot pressure, in relation to untreated controls. Fe-EDTA also improved quality, but did not consistently reduce dollar spot like ferrous sulfate. Sulfur had no effect on turfgrass quality or dollar spot pressure, relative to the control. Infection center counts and visual estimation of percent disease were lowest in plots treated with ferrous sulfate. Ferrous sulfate and Fe-EDTA were statistically similar for infection centers, but percent disease was lower in ferrous sulfate plots. This research demonstrates that the application of ferrous sulfate, but not it’s elemental components, is a viable option to suppress dollar spot epidemics.