2011 Annual Report
Within the first year of this study, we have measured the impact of various timing of crop removal and leaf pulling on vine growth and fruit composition. The crop thinning treatments reduced total vine yield by 40 to 70% compared to non-thinned vines, but it did not increase fruit concentrations of sugars, total color or other quality-related compounds such as tannins and phenolics which are important for mouth-feel and overall wine sensory response. Leaving heavier yields until later in the season did not decrease vine growth of these vigorous vines, and the vines continued to be very vigorous, requiring just as much vine management as earlier crop-thinned vines. Therefore, there is little reason to wait until late in the season to crop thin if it is going to be conducted. Results indicate that there is no fruit quality effect of reducing yields in 2010. Vines were not over-cropped and a full crop load will not hurt the sustainability of the vines.
Within the first year of the leaf pulling trial (2010), we observed little benefit of leaf pulling in terms of fruit composition. While there were differences in cluster exposure with increased leaf removal, there were no differences in berry sugar, acid, tannin, phenolic or color composition. Leaf pulling at the trialed levels did not decrease vine growth and fruit ripening. While little difference was observed in this trial for basic fruit composition and vine growth, the impacts of leaf pulling may be beneficial for preventing fruit rots.
Further analysis of fruit in both the crop load and leaf pulling trials may yield differences in aroma compounds, such as norisoprenoids, which are still under analysis. Further field and lab research continues in 2011 and 2012 to provide additional data from which to draw more solid conclusions and develop metrics for grape growers to make informed decisions.
Methods of project monitoring included meetings, e-mail, and phone calls.