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90 W i n e s & V i n e s M AY 2 0 1 4 Leaves were pulled in order to photograph cluster thinning to one cluster per shoot (left) and two-plus clusters per shoot (right). No leaf pulling occurred on the actual vines studied. WineEast T he production of late-harvest wines provides an avenue for wineries to reach a segment of consumers who may prefer medium-dry or sweet wines. In cool-climate regions, late-harvest wines are typically made from aromatic white Vitis vinifera cultivars such as Riesling or Gewürztraminer that are harvested later in the growing season, when soluble solids ac- cumulation or infection by Botrytis cinerea allow an end product containing natural residual sugar and lower alcohol by volume. The widespread popular belief that low- yielding grapevines produce higher quality wines is entrenched in the late-harvest wine segment because late-harvest wine can be marketed to consumers using scarcity as one of its quality signals. But does this ideology translate to the vineyard? There are two primary costs associated with cluster thinning: skilled human labor and lower revenue from reduced yield. Commercial growers generally cluster thin assuming it will result in quality improve- ments desired by the buyer so that lost revenues may be recouped through higher prices. To assess whether cluster thinning achieves targeted wine characteristics and business objectives, a quantitative and holistic approach to all aspects of yield management including determining whether consumers will have a greater or lesser willingness to pay for the resulting wines was necessary. The New York City metropolitan area is the largest wine market in the United States and consumes approximately 30% of America's total imported wines (Wine Market Council 2009), making it a highly contested market for many quality wine regions. Consumers' wine-drinking habits in New York City are influenced heavily by a specialized niche of restaurant sommeliers, wine writers and wine shop owners who act as market gatekeepers and have specific awareness of New York wines (Preszler and Schmit 2009). Such industry professionals make desirable sensory panelists because they have a robust vocabulary, expert under- standing of important wine attributes and more finely honed sensory acumen than general consumers. To give grapegrowers the best advice regarding optimal cluster thinning and yield-management decisions, it is important to quantify the additional value relationship assumed by buyers conditional to the level of cluster thinning. If a buyer's willingness to pay for wines is differentiated for quality and parallels a grower's cluster-thinning practices, then the grower's minimum price requirements for grapes can be expressed as a function of crop level. A model pub- lished by this research group (Preszler et al. 2010) was the first to position grapevine yield within a quantitative economic decision-making framework. In this study, the model was applied to viticultural and sensory data from a field trial of varying crop levels in a mature com- mercial Riesling vineyard, and the resulting late-harvest wines were panel tested for sensory qualities and willingness to pay Wine East HIGHLIGHTS • A field experiment with cluster thinning was conducted in a Finger Lakes com- mercial vineyard from 2008 to 2010. • The authors investigated whether lower yields would increase the wine trade's willingness to pay. • An expert panel of wine professionals did not prefer wines made from cluster- thinned vines when blind tested against wines from non-thinned vines. Cluster Thinning in Late-Harvest Riesling: Does it Pay? By Justine Vanden Heuvel and Trent Preszler Grapegrowing