Impacts of Early Season Fruit Zone Leaf Removal on Disease Control, Fruit Set, Vine Growth and Grape and Wine Quality of Pinot Noir

Early season leaf removal in the cluster zone can be used as a tool in integrated pest management. The practice of leaf removal is typically conducted in the vineyard after fruit set but before véraison to increase sunlight penetration for fruit development and to enhance fruit quality. Leaf removal at developmental stages prior to bloom may be beneficial in increasing spray penetration for disease control within the grape inflorescence and may also lead to increased fruit quality with increased phenolic precursor production. The study investigates leaf pulling at various growth stages, including flower separation, bloom (50%cap fall), fruit set, pea?sized berries, bunch close, and no leaf pulling. The 2010 season of this study indicates that there is a benefit to leaf pulling early in the season to increase spray penetration of fungicide and to help alter the microclimate to create an environment that is not conducive to Botrytis or powdery mildew infestation. Leaf removal that occurs prior to bunch closure helped reduce disease incidence and severity more than the no leaf pull control. There was a nearly 20 percent reduction in fruit set in pre-bloom treatments at both sites in 2010. This resulted in differences in cluster architecture, including berries per cluster and cluster weight. There were no observed differences in berry weight. Differences in berries per cluster could potentially have acted to reduce disease infection in clusters. This was the first season of this trial where basal leaf removal employed early in the season reduced fruit set. Leaf pulling in the entire cluster zone has not delayed fruit ripening nor total anthocyanins or phenolics. There was no fruit sun-burning observed in any of the leaf pull treatments for the duration of the study despite complete exposure of clusters from pre-bloom though harvest. Continued research into this trial is required to determine the impact of early season leaf removal on disease incidence and secondary effects on fruit quality.