Influence of timing and intensity of fruit zone leaf removal and kaolin applications on bunch rot control and quality improvement of Sauvignon blanc grapes, and wines, in a temperate humid climate

Abstract

Leaf removal is beginning to receive consideration for many growers as an important cultural practice for bunch rots control. It is normally applied after veraison and almost only on red varieties because of the high sunburn susceptibility of white grapes varieties under Uruguayan climatic conditions. The aim of this study was to determine the time and intensity of leaves removal impact on bunch rots and grapes quality on Sauvignon blanc. In parallel, the effects of kaolin (Surround® WP) applications in reducing the negative impact of excessive exposure to high temperatures were evaluated. Different intensities and times of defoliation, in combination with kaolin applications, were evaluated over 2006/07, 2007/08 and 2008/09 seasons. All defoliation treatments and mainly those made after fruit set, significantly reduced the occurrence of bunch rots, having a critical impact on those metabolites responsible for the final taste of wines. Early defoliation was significantly more effective controlling Botrytis incidence and improving berry quality than later in the season. Leaf removal had a determining impact over fruit quality and primary and secondary metabolites contents. An increase in soluble solids and glycosides concentrations was observed, while IBMP grape content was reduced, thus affecting the flavor of Sauvignon blanc wines. Kaolin applications significantly reduced berries temperature, sunburn and other berry damages associated with clusters solar exposure.In sum, leaves removal and exogenous kaolin application in Sauvignon blanc showed great potential as Botrytis mitigation strategy because it positively impacts berry quality as a result of many molecular and biochemical changes in key secondary metabolic pathways. Simultaneously reducing berry sunburn.