Abstract
Emulsions of jojoba wax and canola oil were tested for efficacy against grape powdery mildew (Uncinula necator) and bunch rot (Botrytis cinerea) on two Vitis vinifera grape cultivars ‘Auxerrois’ and ‘Riesling’ over a 2-year period. Jojoba-sprayed (1.0% v/v) ‘Auxerrois’ vines displayed 75-100% reductions in powdery mildew disease severity compared to water-sprayed controls. Both jojoba wax (1.0% v/v) and canola oil (0.5% and 1.0% v/v) also prevented powdery mildew infection in ‘Riesling’, and additionally reduced the incidence of bunch rot in ‘Riesling’ clusters by 68-87%. Jojoba had phytotoxic effects on greenhouse-grown ‘Auxerrois’ vines during periods where temperatures exceeded 35°C. However, vine vigor, yield, and berry composition of field-grown vines were not adversely affected. Tasters were unable to distinguish between ‘Auxerrois’ wines produced from jojoba and Kumulus (flowable sulfur) treatments. Jojoba and canola oils reduced berry and must titratable acidity and increased berry, must and wine pH. Tasters distinguished between wines from canola and Kumulus treatments, and found canola wines had more intense ‘Riesling’ aroma. Although further testing is required, jojoba and canola emulsions show promise as prophylactics of powdery mildew and bunch rot in grapevines.
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