Salvia officinalis Extract Can Protect Grapevine Against Plasmopara viticola

The ability of sage (Salvia officinalis) extract to control grapevine downy mildew under greenhouse and field conditions was tested. The persistence and rainfastness of sage extract were also investigated. Sage extract provided a high level of sustained disease control in artificially inoculated, potted grapevine under greenhouse conditions. However, even small amounts of simulated rainfall (10 mm) significantly reduced efficacy of sage extract. In a field experiment in 2006, sage extract provided 94% reduction in disease incidence and 63% reduction in area under the disease progress curve for disease severity on berries and leaves, respectively, reaching a level of disease control not significantly different from that provided by copper hydroxide. In 2007, the sage extract provided only a partial reduction (less than 30%) of downy mildew on leaves, probably as a result of a long rainy period between two of the consecutive treatments. Overall, sage extract effectively controlled grapevine downy mildew and could be a promising alternative to copper in organic viticulture. However, the low rainfastness of this treatment adversely affected its efficacy.