How vineyard features and application time may affect the phosphonates residues in the bunches

Abstract: Phosphonates are widely used to control grapevine downy mildew (Plasmopara viticola) due to their high efficacy and the good toxicity and eco-toxicity profile. They were often commercialised as fertilisers (phosphorus) but they are not metabolized by the plant and residues are found in the plant tissues. The antifungal mode of action is not fully understood, however they are easily translocated in the plant and accumulation can result in high levels of residues in the grapes.A two-year field trial investigated the influence of the vineyard features, agronomic practices and the application time on residues accumulation of phosphonates in bunches. The main factor that affects the residue accumulation in the grape is the application time of phosphonate. Vineyard vigour, variety and canopy management have only a slight effect on the residues. Further studies are needed to understand the role of weather conditions on the phosphonate residues.