Use of biostimulants as an alternative to synthetic chemical plant protection products

Abstract

The control of grapevine fungal diseases such as powdery mildew (Erysiphe necator) and downy mildew (Plasmopara viticola) traditionally relies on sulfur- and copper-based products. Although effective, the repeated use of these compounds raises environmental concerns, particularly regarding copper accumulation in soils and its impact on ecosystem sustainability.

This study evaluates the use of a biostimulant-based strategy as an alternative or complement to conventional plant protection products in organic viticulture. The trial was conducted over several growing seasons in a rainfed vineyard of Vitis vinifera L. cv. Red grenache located in the Priorat region (Tarragona, Spain). Three treatments were compared: conventional sulfur and copper applications, a biostimulant treatment free of sulfur and copper, and an untreated control.

Disease incidence and severity of powdery mildew and downy mildew were monitored throughout the season. In addition, soil and leaf nutritional status, vegetative growth, grape ripening parameters, and wine composition and sensory attributes were assessed.

Disease pressure varied markedly between years. In seasons with low or absent downy mildew pressure, the biostimulant treatment showed comparable performance to conventional management, allowing a reduction or substitution of copper-based applications. Similarly, under low powdery mildew pressure, the biostimulant contributed to reducing the number of sulfur treatments. No negative effects on vine vigor, grape ripening, or wine quality were observed.

These results suggest that biostimulants can be a valuable tool within integrated and organic vineyard management strategies, contributing to a reduction in conventional fungicide use and supporting more sustainable viticulture under variable climatic conditions.