Crop Load Adjustment In Vitis Vinifera L. Cv. Riesling

Cluster thinning is practiced to reduce grapevine crop load and advance ripening parameters, such as soluble solids, which may or may not lead to higher quality wine. It is often implemented in the field with little or no specificity, and its practicality has been questioned because of increased production costs and lost yields. A new analytical model was introduced that combines grapevine yield and cost data with an assessment of wine quality and willingness to pay (WTP). The model was applied to two separate but concurrent field studies whereby crop levels of 1 (low), 1.5 (medium), and 2 (high) clusters per shoot established by cluster thinning (CT) were compared to non-thinned (control) Riesling vines over a three year period in the Finger Lakes of New York. In both studies CT enhanced soluble solids accumulation and had effects on yield components mostly consistent with previous literature. Consumer wine sensory trials revealed that lower cropped vines (crop load below 5) produced wines with different aromatic attributes and lower likability ratings than wines from higher crop levels. The reduced financial net returns experienced by grape growers at lower vine crop levels could only be offset by substantial increases over base market price for grapes. However, consumer WTP trended inversely with grower net returns indicating per-bottle price increases could not be used to offset the financial losses associated with CT. Despite enhancements to fruit maturity, the extreme application of CT is not a justifiable component of a sustainable viticulture program for viticultural, enological, wine quality, and financial reasons