Influence of Ferrous Sulfate and Its Elemental Components on Dollar Spot Suppression

Abstract

Dollar spot (caused by Sclerotinia homoeocarpa F.T. Bennett) is a common disease of Agrostis stolonifera L. and is especially devastating on putting greens. Sequential fungicide applications are often required throughout the growing season for adequate control. This research was conducted to determine if ferrous sulfate (FeSO4) and its elemental components are capable of reducing dollar spot development. Trials were established in situ and in vitro to address this objective. Putting green trials were conducted in Blacksburg, VA, during the summers of 2012 and 2015. Biweekly (May to September) foliar treatments were applied in four randomized complete blocks as: control, FeSO4 (48.8 kg ha−1), sulfur (10.3 kg ha−1), and iron chelate (11.2 kg Fe ha−1). Dollar spot infection centers and visual turf quality were recorded throughout the summer. When disease exceeded a threshold of 75 infection centers per plot, chlorothalonil (2,4,5,6‐tetrachloroisophthalonitrile, 12.5 kg ha−1 a.i.) and nitrogen fertility (12.2 kg ha−1) were applied to encourage recovery. After recovery, inputs were minimized to encourage dollar spot development. Ferrous sulfate reduced dollar spot pressure each year. Turf quality was improved with FeSO4 in 2012, but not in 2015. Iron chelate suppressed dollar spot in 2012, but not in 2015. Sulfur had no impact on dollar spot or turf quality in either year. Direct fungitoxic activity of FeSO4 against the dollar spot pathogen was evaluated in vitro across a range of pH. Pure cultures of S. homoeocarpa obtained from the field test site were plated on 0.25× potato dextrose agar amended with 0, 10, 100, and 1000 mg kg−1 FeSO4. Mycelial growth was enhanced at 10 mg kg−1, was not affected at 100 mg kg−1, and was completely inhibited at 1000 mg kg−1. These data suggest FeSO4 suppresses dollar spot by acting as a fungistat against the pathogen.

Alternative and Low-Use-Rate Herbicides Offer Similar Levels of Weed Control to Current Standards in Turfgrass Lawns in the Upper Midwest

“…Caution should be exercised when using Fiesta to avoid possible iron toxicity injury to desirable grasses. Iron toxicity has been observed on annual bluegrass under golf course conditions in both Oregon (Mattox et al, 2017) and Virginia (McCall et al, 2017). No injury to desirable grasses was observed in our study.…”

Iron homeostasis and plant immune responses: Recent insights and translational implications

“…Excess iron could also nullify the benefits that siderophores provide by mitigating oxidative stress (76). Interestingly, exogenous application of iron suppresses disease in turfgrass by mechanisms that are currently unknown but may be due to production of ROS as in maize (163) or repression of iron uptake from the rhizosphere as seen after exogenous application of iron to plant shoots (164). Finally, manipulation of the soil microbiome holds great promise for simultaneously enhancing iron uptake and promoting disease resistance, although the interactions between beneficial microbes and iron-biofortified crops remain to be thoroughly explored (115,119).…”

Impact of ferrous sulfate concentration on Clarireedia isolate growth and dollar spot development

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