Vitis vinifera planting in Michigan is increasing by 10% per year. Red varieties are currently the main focus and challenge for the Michigan wine industry, since it is hard to get these varieties to reach full maturation at harvest. The objectives of this study were to improve the fruit quality and subsequent wine sensory characteristics of Cabernet Franc by applying different viticultural practices aimed at reducing typically high levels of 3-isobutyl-2-methoxypyrazine (IBMP) in this region.Experiments conducted in 2010 and 2011 evaluated different levels and timings of cluster thinning and leaf removal from the basal nodes. In 2010, cluster thinning increased the pruning weight and cluster weight, and had insignificant impact on basic fruit chemistry at harvest. In both years, neither cluster thinning nor leaf pulling were significantly affecting vegetative growth. In 2011, cluster thinning did not have a significant impact on vine vigor and basic fruit chemistry, but did reduce the IBMP level by 17%. Leaf removal decreased the titratable acidity by 10% and IBMP level by 35%, but had no effect on other basic quality parameters. Leaf removal and cluster thinning not only increased the anthocyanins content, but also the efficiency of anthocyanins accumulation expressed as the ratio of anthocyanins to sugar. In addition, more uniform fruit quality has been achieved by early leaf removal.
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