Leaf Removal: a Tool to Improve Crop Control and Fruit Quality in Vinifera Grapes

Research Date
Paolo Sabbatini, Glen Greiffendorf
Best Practices, Crop Quality
Crop Categories
Beverage Categories

Cool and humid climate in Michigan limits technological fruit maturity at harvest as evidenced by cluster-rot and poor ripening. Economically important wine grape varieties in Michigan have high susceptibility to harvest season cluster rot. Important cultivars that are particularly susceptible are Riesling, Chardonnay, Pinot blanc, Pinot gris, Pinot noir (Vitis vinifera L.). A detrimental characteristic common to all of these varieties is the compactness of the berries held on the cluster rachis.

The aim of this work is to determine whether a quantified amount of leaf removal at bloom would reduce fruit set and consequently produce a controlled reduction in cluster compactness. Research reports have shown in a three-year survey that both pre- and post- bloom hand and mechanical defoliation are effective in limiting yield by means of reducing the number of berries per cluster on a high-cropping cultivar. Cluster size was also reduced while improving must soluble solids and total anthocyanins on a fresh-weight basis.

Our study was conducted to 1) verify whether early leaf removal can be consistently used as a tool for controlling cluster bunch rot through reducing cluster compactness on Riesling and determine the effects of leaf removal on grape quality (skin/flesh ratio, color and basic fruit chemistry parameters).

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