Development of a quantitative tool for environmentally sustainable copper fungicide application and tracking within vineyards

Abstract

Copper-based fungicides (CuFs) are used in vineyards and fruit-farms as a preventive form of pathogen control. These have a fungicidal impact against mildew infections (Plasmopara viticola) and other fungi that attack grapevines causing poor plant development, fruit rot, and ultimately, poor wine production. If applied annually in large quantities, copper pollutes both the vineyard soil and the surrounding freshwaters. This research combines a copper soil transport model within vineyard systems, a downy mildew germination model, and a copper dosage model with the ultimate aim of diminishing copper usage to concentrations as low as reasonably achievable while determining its environmental fate. The copper soil transport model is based on a solid-solution partitioning model, water balance model, and biotic ligand model. The downy mildew model is built according to a mechanistic model which separates the morphological development of mildew into discrete variables. The copper dosage model is built by combining a grapevine development model, a spray efficiency model, and a deposition efficiency model. Running the simulation from 2009 to 2018 for a vineyard in the Bordeaux Graves region, the model predicts that copper usage could have been reduced to 4.7 kgCu*ha-1 annually by only applying during mildew infection events and accounting for leaf area dependent spray deposition rates. Improving spray efficiency by 10% could further reduce copper demand to 3.9 kgCu*ha-1, below the new European limit of 4 kgCu*ha-1. Soil pH and organic matter adjustments most affected copper speciation, controlling biological uptake rates, soil matrix storage, and leaching rates; while varying the clay content did not present significant impacts.