Wines & Vines

GRAPEGROWING LATERAL CROP PRODUCTION Leaf removal reveals yellowing leaves in this dense canopy Pinot Noir vine. Excess canopy growth and presence of lateral crop are evidence of high vine vigor. Vine rebellion against imbalance photos by Patty Skinkis BY Dr. Patty Skinkis, viticulture extension specialist, and Alison Reeve, viticulture Ph.D. student, Oregon State University, Corvallis, Ore. V ine balance is often discussed in the context of vineyard management and research, assuming that balance is something that can be controlled. However, vines are biological beings with their own physiological drives that are dependent upon both genotype and environment. As a result, vine balance can only be managed, not controlled. This is evident when we consider the variability observed in Oregon for fruit set and yield across several years. The 2012 growing season had variable fruit set across the state, and many producers reported lower than normal fruit set and reduced yields at harvest. Reduced set was due to many factors, ranging from rainy weather during bloom, inflorescence necrosis or hail damage. Unfortunately, narrowing down one factor to blame for fruit set issues Grape clusters develop on lateral shoots of Pinot Noir in 2012. and low yield is neither fair nor possible, making prophylactic management in the vineyard difficult to avoid these shifts in fruit set from year to year. Based on the reported yields for Oregon wine grapes from 1990 to 2011, there is a reduction in yield on an average of every four years.7 This could be influenced by several factors, but it is likely that the lower yield years coincide with incidences of reduced fruit set that is a function of vine health and environmental conditions. Since most Pinot Noir vineyards in Oregon are managed to achieve target yields between 2 and 3 tons per acre, one could question why we should care about the amount of fruit that is set, especially if low fruit set means reduced clusterthinning costs. Like most grapegrowers, Oregon producers want adequate yield for economic stability. They need enough fruit set to make adjustments to achieve optimized yield targets that they relate to final wine quality. For this reason, it is important to look at the various factors influencing yield. Natural yield reduction can occur at the level of the shoot (number of clusters per shoot), inflorescence (number of florets per inflorescence pre-bloom) or individual flowers (poor pollination and fertilization). Based on research gathered during the past few years in Oregon, weather was found to be only a small part of the story when it comes to fruitfulness and fruit set. Pinot Noir has relatively low fruitfulness, defined as the number of inflorescences per shoot. Based on data from various cane-pruned Pinot Noir vineyards in Oregon (2008–12), the average number of clusters per shoot is 1.6. Research and practical experience show that there can be reduced fruitfulness in vines with high vine vigor and canopy density. Peter Dry and Brian Coombe of Australia associated reduced fruitfulness in Shiraz with vine vigor (measured as cane diameter).4 In their work, they found increased primary bud necrosis in shoots with thicker canes (more than 12 mm diameter), and this resulted in more secondary bud growth and reduced cluster production as secondary buds typically have fewer flower primordia and result in fewer clusters per shoot. pr actica l win ery & vin eya rd AU GU ST 20 13 81

• Cover