The Efficacy of JMS Stylet-Oil on Grape Powdery Mildew and Botrytis Bunch Rot and Effects on Fermentation

Abstract

The use of JMS Stylet-Oil as a control for powdery mildew and bunch rot of grapes was investigated under California vineyard conditions. Stylet-Oil at 2% (v/v) was compared in commercial vineyards with commonly used fungicides including fenarimol, myclobutanil, triflumizole, and sulfur for powdery mildew control, or iprodione for bunch rot control. Stylet-Oil gave control of powdery mildew comparable to the demethylation inhibitor fungicides. Botrytis bunch rot was significantly reduced with Stylet-Oil alone, and when Stylet-Oil was mixed with iprodione a further reduction in bunch rot occurred. Grape juice fermentation as measured by yeast growth and sugar consumption was not affected by Stylet-Oil concentrations that ranged from 0 to 3.6 mL/L.