Timing and Intensity of Grapevine Defoliation: An Extensive Overview on Five Cultivars in Switzerland

Abstract

This article synthetizes the observations from five experiments and brings practical results about the effects of the timing and intensity of defoliation on white and red Vitis vinifera cultivars. – Pinot noir, Gamay, Merlot, Chasselas and Doral. Intensive defoliation (removal of 6 basal leaves + 6 lateral shoots per shoot) was completed at three developmental stages of the grapevine, i.e., preflowering, flowering and bunch closure. Preflowering defoliation had tremendous consequences on vine agronomic performance, mainly to the detriment of berry set; the yield was highly affected by preflowering defoliation (approximately −35 % in comparison with no defoliation). The intensity of defoliation allowed its impact on the yield to be modulated. The intensity of defoliation also had a positive impact against millerandage, sunburn symptoms and Botrytis cinerea development. The berry skin thickness doubled, and the polyphenol concentration significantly increased with preflowering defoliation. Due to preflowering defoliation, the red wines were often preferred for their color and mouthfeel. However, this practice had a negligible impact on white wine composition. Regardless, preflowering defoliation did not have a negative impact on wine parameters. In the context of this study, preflowering defoliation seems to be an interesting technique to reduce vigor and control the high production potential. Preflowering defoliation also represents a prophylactic solution to reduce both chemical applications and cluster-thinning costs.