The objective of this work was to investigate the effects of earliness and intensity of defoliation on five Vitis vinifera cvs. – Pinot noir, Gamay, Merlot, Chasselas and Doral – under the mild-climate conditions of Switzerland. Between 2010 and 2016, intensive defoliation (removal of 6 basal leaves + 6 lateral shoots per shoot) was completed at three developmental stages of grapevine, i.e., pre-flowering, late flowering and bunch closure. Chasselas experiment also had a moderate pre-flowering defoliated treatment (removal of 3 basal leaves). In addition to the vintage effect, pre-flowering defoliation had tremendous consequences on the vine agronomic performance, mainly to the detriment of berry set: the yield was highly affected by the pre-flowering defoliation (approximately -30 % in comparison with no defoliation). The intensity of defoliation allowed the modulation of the impact on the yield. It also had a positive impact against millerandage, sunburn symptoms and Botrytis development. Berry skin thickness doubled and polyphenol concentration increased significantly. Due to pre-flowering defoliation, red wines were often preferred for their colour and structure in mouth. Meanwhile, this practice had negligible impact on white wine composition. In any case, pre-flowering defoliation did not have any negative impact on the wine parameters. In the context of this study, pre-flowering defoliation seems to be an interesting technique to reduce vigour and control high production potential. It also represents a prophylactic solution to reduce both chemical entrants and cluster-thinning costs.
