Manual and mechanical leaf removal in the bunch zone (<em>Vitis Vinifera</em> L., cv Barbera): effects on berry composition, health, yield and wine quality, in a warm temperate area

Abstract

<p style="text-align: justify;"><strong>Aims</strong>: The main objective of the fruit zone leaf removal is the microclimate improvement around fruits in order to enhance grape ripening and fruit health. The aim of this work was to investigate the consequences of manual or mechanical leaf removal according to the phenological stage (fruit set or véraison) on spraying efficiency, yield composition, berry colour, must and wine quality, and grape health.</p><p style="text-align: justify;"><strong>Methods and results</strong>: A three-year experiment (2001-2003) on the cv. Barbera was carried out in northwest Italy. Weather conditions during the three experimental seasons were very different. Leaf removal improved the efficiency of the fungicide application, reducing fungal diseases, but increased grape sensitivity to sunburn due to greater sunlight exposure. Some significant decrease on yield components was observed but not because of the same treatment. In leaf-removed vines, berry quality increased in the year least favourable for ripening (2002); in the warmer years, no quality improvement in must and wine was observed.</p><p style="text-align: justify;"><strong>Conclusion</strong>: Leaf removal effects are not strictly tied to intervention time; the main effects were due to the vintage weather conditions: in unfavourable ripening conditions, leaf removal can improve grape health and quality. Due to the higher level of bunch temperature induced by this technique, in warmer conditions its usefulness needs to be accurately evaluated. Although a faster process, mechanical leaf removal did not provide any substantially different results when compared to manual intervention.</p><p style="text-align: justify;"><strong>Significance and impact of study</strong>: The study showed potential and limits of leaf removal, suggesting that his application may vary, depending on climate and weather conditions of vineyards and vintage.</p>