Evaluation of essential plant oils for the control of Plasmopara viticola

The aim of this study was to test the effectiveness of various concentrations of tea tree oil and clove oil against Plasmopara viticola. In vitro tests entailed assessing the development of P. viticola on leaf disks and calculating sporangial germination. In a field trial, formulated products containing 23.8% tea tree oil (BM-608) and 15% clove oil (Sporatec) were tested in an organic vineyard to control downy mildew. The efficacy of pure and formulated essential oils was compared with a water control and a reference product (Airone, containing copper oxychloride 50% and copper hydroxide 50%). Laboratory experiments revealed the inhibitory activity of essential oils, although the effectiveness was lower than that of the reference product. The field data demonstrated that BM-608 and Sporatec were able to control the development of downy mildew although they were not as effective as the reference product. This study suggests the application of essential oils in order to reduce the use of synthetic pesticides in agriculture, in accordance with European laws, and to avoid the environmental pollution of copper in organic farming.