Leaf-Removal Effects on Cynthiana Yield, Juice Composition, and Wine Composition

Abstract

Cynthiana (Vitis aestivalis Michx.) grapes typically have high acidity (8.5 to 13 g/L as tartaric) and high pH (3.4 to 3.8) at harvest. The must is high in malic acid (4 to 6 g/L), and the wines normally undergo malolactic fermentation, which further increases pH. Leaf-removal treatments were applied for four years to determine if leaf removal would affect yield or fruit or wine composition. Vines trained to a single high-bilateral cordon in northsouth rows were used to establish three leaf-removal treatments: no leaf removal, leaf removal on east side of canopy, and leaf removal on east and west sides of canopy. Leaf removal was applied in a 36-cm fruiting zone when berry size reached 7 mm. Year had the greatest impact on yield, fruit composition, and wine composition of any of the variables studied. Leaf removal did not affect yield or yield components in any year and had little or no impact on juice composition in 1997 or 1999. Wines had darker and increased red color, in all years, when made from fruit of vines that had leaves removed. In 2000, a year with 13 consecutive days of temperatures 35°C or above during veraison, leaf removal was a successful tool to reduce pH and malic acid in Cynthiana grapes. There was no advantage to removing leaves from both the east and west sides of the canopy as opposed to removing leaves from the east side only.