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Development of a botanical plant protection product from Larix by-products to protect grapevine from Plasmopara viticola

Lucius Tamm: Research Institute of Organic Agriculture FiBL

<div>BACKGROUND: Plant extracts might provide sustainable alternatives to copper fungicides, which are still widely used despite<br /="/">their unfavourable ecotoxicological profile. Larch bark extract and its constituents, larixyl acetate and larixol, have been shown<br /="/">to be effective against grapevine downy mildew (Plasmopara viticola) under semi-controlled conditions. The aim of this study<br /="/">was to reduce the gap between innovation and the registration of amarketable product, namely to develop scalable extraction<br /="/">processes and to evaluate and optimise the performance of larch extracts under different conditions.<br /="/">RESULTS: Toxicologically and technically acceptable solvents like ethanol were used to extract the active compounds larixyl<br /="/">acetate and larixol from bark in sufficient amounts and their combined concentration could be increased by up to 39% by<br /="/">purification steps. The combined concentration of larixyl acetate and larixol from larch turpentine could be increased by up to<br /="/">66%.TheMIC100 againstP. viticola in vitro (6-23 𝛍gmL-1)andtheEC50 in planta under semi-controlled conditions (0.2-0.4mgmL-1 Q4 )<br /="/">were promising comparedwith other plant extracts. In vineyards, efficacies of larch extracts reached up to 68% in a stand-alone<br /="/">strategy and 84% in low-copper strategies.<br /="/">CONCLUSION: Larch extracts represent valid candidates for copper reduction in organic vineyards, and their development into<br /="/">a sustainable plant protection productmight be feasible.</div>