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Home HortTechnology Crop Load Adjustment Strategies Compared in 'Seyval Blanc' Winegrape
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ITHACA, NY--More isn't always better, at least to winegrapes growers. For instance, 'Seyval Blanc', a cold-hardy variety favored in the Finger Lakes region of New York and other viticulture regions in eastern North America, is known for its proclivity to overproduce. The popular cultivar can produce too much fruit, which in turn decreases grape quality, and its vines do not respond well to typical pruning techniques that generally moderate the amount of fruit produced.

A team of researchers from Cornell University designed a study to compare crop reduction techniques' effects on fruit, yield, consumer preference, and the bottom line for winegrape growers. The findings were published in HortTechnology.

Cornell researchers Tyler Berkey, Anna Katharine Mansfield, Steven Lerch, James Meyers, and Justine Vanden Heuvel reported on experiments using four crop reduction treatments in plots in an Ovid, New York, winery. The control plot of 'Seyval Blanc' received no treatment. The second received a treatment called shoot thinning, where some fruit-bearing shoots were removed from the vine. The third plot was treated by removing some clusters from fruiting shoots, while the fourth plot received both shoot thinning and cluster thinning.

The team performed shoot thinning when shoots were about 2 to 5 inches in length and thinned to 15 shoots per meter. Cluster thinning took place when grapes were about the size of peas so that each shoot contained only two clusters of grapes. At harvest, they counted the number of clusters per vine and measured yield per vine. Grapes from each treatment were made into wine, then evaluated by a panel of tasters.

The first year of the study, shoot and cluster thinning reduced the yield and the number of clusters per vine compared to the control. The average cluster weight was higher for shoot-thinned vines than the control, but cluster thinning had no impact. The second year of the study resulted in yield, cluster number, cluster weight, and crop load not being impacted by cluster thinning, which "likely differed between years due to the carryover effects of the treatments," according to the study.

The tasting panel reported a preference for wine produced by the cluster thinned grapes in the first year, with shoot thinning plus cluster thinning grapes taking second place. However, this was similar to the control. None of the four wines produced in the second year stood out as a clear preference. The researchers suggested that the cooler and wetter growing season of the first year made the effects of thinning more pronounced.

The techniques investigated in the study come with a price to growers. "To cover the costs of cluster thinning in a growing season like the first year, the price would need to increase from $556/metric ton to $824/metric ton, which would be passed on to consumers at an additional $0.41 per 750 mL bottle of wine," the report said. The combination of shoot and cluster thinning comes at an even higher price of an extra $0.71 per 750-mL bottle.

"In growing seasons like the second year, thinning would not be economical because it did not result in wine preferred over the control", the study said. "Crop load reduction techniques may only be economically justified if crop load is extremely high (such as in the control treatment the first year), and/or during poor growing seasons."

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The complete study and abstract are available on the ASHS HortTechnology electronic journal web site: http://horttech.ashspublications.org/content/21/5/593.abstract

Founded in 1903, the American Society for Horticultural Science (ASHS) is the largest organization dedicated to advancing all facets of horticultural research, education, and application. More information at ashs.org


 

Original Article:

Crop Load Adjustment in 'Seyval Blanc' Winegrape: Impacts on Yield Components, Fruit Composition, Consumer Wine Preferences, and Economics of Production
Tyler G. Berkey, Anna Katharine Mansfield, Steven D. Lerch, James M. Meyers, and Justine E. Vanden Heuvel
HortTechnology 21:593–598. [Abstract][Full Text][PDF]

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