Essential oils to successfully reduce copper fungicide in vineyard
Résumé
Copper is the only authorized fungicide in organic vineyard to control plasmopara viticola, a fungus that causes important harvest loss. Nevertheless, copper is a non-degradable heavy metal and its accumulation in topsoil has a negative impact on the growth and development of most plants, microbial communities and soil fauna (http://institut.inra.fr/en/Objectives/Informing-public-policy/Scientific-Expert-Reports/All-the-news/Can-organic-farming-manage-ithout-copper, 03/20/2018). These effects have lead to using alternatives methods in order to reduce copper use in viticulture. In this context, we propose to spray a combination of fruity essential oils and bees propolis and copper reduction to control Plasmopara viticola in the vienyard. For that reason, a sustainable innovative system (SIS) has been designed (Metral et al., 2015). The aim of this presentation is the design, the implementation and the assessment of the experimentation of the SIS. The experimental plot planted in 1996 is a vineyard in the northeast of France. It meets organic farming certification. Essential oils uses were : organic sweet orange and organic grapefruit seeds combined to propolis (natural resin used by honeybees to repair and clean the beehive). This experient, performed in a standard way, was assessed in compliance with agronomic and environmental indicators. The elements used to perform the assessment were the yield (quality and quantity) and the vigor (wood weight). Environmental assessment was conducted through TFI (Treatment Frequency Index) data and I-Phy indicator from the INDIGO method (Thiollet-Scholtus and Bockstaller, 2015). The outcome is the design of the SIS according to a system-experiment with the participation of some winegrowers who made some of their plots available and suggested interesting innovations. Agronomic data show that the targeted yield and quality were reached every year for five years (2013-2016). Fungi attacks at harvest were acceptable compared to the reference. The final outcome on theenvironmental assessments is really satisfying : (i) Copper use is 6 to 12 times reduced comparing to the reference. (ii) TFI is between 2 and 7 depending on the year, when regional average is 13. (iii) I-Phy indicator is about 9.9 every year, with a scale from zero (maximum risk) to 10 (no risk). In conclusion, this SIS has proved efficient in terms of environmental issues to solve (reduction of copper rate in vineyard).