Intensity and timing of defoliation on white cultivar Chasselas under the temperate climate of Switzerland

Aim: The objective of this work is to investigate the effects of early defoliation on cv. Chasselas under the temperate conditions of Switzerland, with particular attention to berry anatomical traits and wine sensory parameters. Methods and results: Defoliation (removal of 6 basal leaves + 6 lateral shoots per shoot) was completed during three developmental stages of grapevine, i.e., pre-flowering, late flowering and bunch closure, and at two intensity levels. The experimentation was performed repeatedly over four years. In addition to vintage effect, pre-flowering defoliation had a consistent impact on vine agronomic behaviour. The yield was highly affected by the technique (more than 30% loss). Earlier and more intense defoliation had more impact on yield, while post-berry-set defoliation had no effect on yield. Intensive defoliation also modified berry skin thickness and had a positive impact inhibiting Botrytis development. Wine composition and sensory analysis were not affected by the practice. However, pre-floral defoliation affected bud fruitfulness and vigour, i.e., trimming and pruning weights. This result noted a carryover effect that could affect vine sustainability under restrictive conditions. Conclusion: In the context of this study, pre-flowering defoliation seems to be an interesting practice to reduce vigour and control the high production potential of the cv. Chasselas. The intensity of early defoliation allows for the modulation of the impact on the yield in order to prevent excessive yield loss. Significance and impact of the study: Pre-flowering defoliation of the white cultivar represents a prophylactic solution to reduce both chemical entrants and bunch-thinning costs