An evaluation of biological and abiotic controls for grapevine powdery mildew, 1. Greenhouse studies

Grapevine powdery mildew, caused by the fungus Erysiphe necator, is a major disease affecting grape yield and quality world-wide. In conventionally-managed vineyards, this disease is controlled mainly by regular application of sulfur and synthetic fungicides; and in organic agriculture, by sulfur and canola-based oils. Health and environmental impacts associated with the use of sulfur, development of resistance to certain synthetic fungicides, and demand for residue-free grapes, all point to a need for effective alternatives to sulfur and synthetic chemicals. Accordingly, seven greenhouse experiments were conducted to evaluate the potential of novel (abiotic) materials, as well as certain biological agents, for controlling powdery mildew. Application of Bacillus subtilis, milk (200 mL/L), whey (30 g/L), canola-based oils (2-4 mL/L) and Ecocarb (potassium bicarbonate, 3 g/L) all reduced the severity of powdery mildew, and in some cases by 96% compared with untreated controls. Such treatments thus offer potential as alternatives to sulfur in organic viticulture if their efficacy can be duplicated under field conditions - the subject of paper 2 in this series (Crisp et al. 2006, Australian Journal of Grape and Wine Research 12, pp. 203-211).