Speaker: Dr. Stefano Musacchi, Associate Professor & Endowed Chair, Tree Fruit Physiology and Management, Washington State University Affiliation: WSU Tree Fruit Research and Extension Center, Wenatchee, WA 98801-1230 Synopsis: Dr. Musacchi introduces the concept of organ competition as it relates to both vegetative growth and fruit production and how pruning influences these responses. He introduces three new terms including brindilla (one year old shoot with terminal flower bud), Tira savia (pruning technique to induce a strong response in the apical part of the branch and minimize suckering and production of blind wood), and chicken paw or zampe di gallo (an old spur formation that produces small fruit when they become too weak). He emphasizes the fact that small-sized flower buds result in small-sized fruits. He also introduces the five different tree growth habits of fruit bud production for pear cultivars. Bartlett is Type 1 which is comprised primarily of 2-year-old branches with brindilla and spurs. Dr. Musacchi speaks about pruning spindle trees and the importance of bending branches to a maximum of a 45-50 degree angle from the vertical axis to avoid weak branches and the production of blind wood. He also introduces the concept of dynamic or renewal pruning and a three-year cycle. This involves a rotational strategy to produce new wood, develop 1-year-old wood and produce fruit on 2-year-old wood. He emphasizes the importance of using primarily 2 or 3-year-old wood that is fairly close to the central axis of the tree for production of large, high-quality fruit. Dr. Musacchi demonstrates using both girdling and notching to remove apical dominance and stimulate lateral branching in 2-year-old wood to avoid the production of blind wood. Dr. Musacchi introduces the practice of using growth regulators to influence tree response to girdling and notching (e.g., combination of gibberellin plus cytokinin). Dr. Musacchi speaks about the 30 percent rule (remove branches attached to main axis when their diameter exceeds 30 percent of the diameter of the main axis). He notes that the tip of the branch should be higher than its insertion in the main axis. Dr. Musacchi demonstrates how to prune young spindle trees and also how to manage the top of the tree. He also demonstrates how to manage trees that are different heights going down the tree row. Dr. Musacchi also demonstrates spindle pruning of mature trees and the need to make the three-year cycle of renewal pruning. Finally, he introduces the bi-axis (or Bibaum) training system to reduce excess vigor and to double the number of axes in the row without doubling the number of the trees.

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