Impact of Shoot and Cluster Thinning on Yield, Fruit Composition, and Wine Quality of Corot noir

Abstract

Cluster thinning (CL), shoot thinning (ST), and a combination of the two practices (ST+CL) were applied to vigorous Corot noir (hybrid sp.) winegrapes grown at a commercial vineyard in the Finger Lakes region of New York State. Yield was reduced by CL (by up to 4.8 kg/vine) but not ST in 2008, and by ST (by up to 2.0 kg/vine) and not CL in 2009; however, high pruning weights (up to 4.5 kg/vine in 2008) and low crop-load ratios (ranging from 2.3 to 7.1) indicated that vines in the study were undercropped regardless of treatment. CL increased soluble solids by up to 2.5 Brix in 2008 and by up to 0.8 Brix in the ST+CL treatment in 2009, while ST increased soluble solids in 2009 by 0.8 Brix. The treatments had variable impacts on wine anthocyanin, berry skin tannin, berry seed tannin, and wine tannin depending on year. Wine tannin (42 to 64 mg/L) and tannin extractability (5 to 6%) were both very low compared to values typically observed in red wines produced from V. vinifera. Using a two-alternative forced choice test, panelists reported ST+CL wines were fruitier than the control and ST wines and that ST wines were less fruity than the control in both years. An economic analysis indicated that in order for growers/wineries to maintain their economic welfare, bottle prices would have to increase by $0.02 to $0.41 depending on the practice and year to compensate for additional labor costs and lost yield in implementing these crop-load management practices.