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Effects of anaerobic soil disinfestation on Sclerotinia sclerotiorum and Sclerotinia minor in Ohio muck soil

Andres Sanabria: The Ohio State University

<div>Intensive lettuce production on muck soils leads to the buildup of <em>Sclerotinia sclerotiorum </em>and <em>S. minor</em>, causal agents of lettuce drop. The effects of anaerobic soil disinfestation (ASD) on <em>S. sclerotiorum</em> and <em>S. minor</em> were evaluated under growth chamber and field conditions. In growth chamber trials, ASD amendments molasses, wheat bran, and mustard greens at 20.2 t/ha and a 2% ethanol solution were tested in experiments designed to determine the effects of volatile compounds produced during ASD on mycelial growth and production of sclerotia. Amended, flooded muck soils were placed in the bottom of petri dishes and covered with another petri dish bottom with PDA medium and an inoculum plug of <em>S. sclerotiorum</em> or <em>S. minor</em>. Petri dishes were sealed with two layers of parafilm. Significant reductions in the number of sclerotia produced and mycelial growth of <em>S. sclerotiorum</em> and <em>S. minor</em> were observed for wheat bran, molasses and ethanol compared to the non-amended, flooded control. Field trials were conducted in plots amended with wheat bran (20.2 t/ha), molasses (10.1 t/ha), or wheat bran (20.2 t/ha) + molasses (10.1 t/ha), then flooded and covered; controls were not amended, but flooded and either covered or uncovered. Sclerotia of both pathogens were buried in treated soils and recovered after 4 weeks to assess their viability. Significant reductions compared to the controls in viability of sclerotia of both pathogens were observed for all carbon sources.</div>