Effect of Calcium, Boron and Naphthalene Acetamide Sprays on Cork Spot and Mineral Content of York Imperial Apple1

Abstract

Abstract Boron, calcium, and naphthalene acetamide (NAAm) foliar sprays were applied alone or in combination to ‘York Imperial’ apple trees under Eastern Pennsylvania orchard conditions. Mineral content of the leaves and fruit and number of cork spots in the fruits were determined. B applications alone or in combination with Ca and/or NAAm increased leaf and fruit B content. All Ca applications increased the leaf Ca content, the fruit P content, and the leaf and fruit K and Fe content, but had no effect on fruit Ca content. NAAm sprays increased the leaf Mg and Al content. NAAm applied in combination with Ca increased the leaf Ca content. The NAAm effects appear to be associated with the valence of the element, having no effect on monovalent elements, some effect on divalent elements, and the strongest effect on the trivalent element, Al. Th B-Ca and B-Ca-NAAm spray treatments reduced the number of cork spots per fruit. Regression analysis indicated that as the B and Ca content increased in the leaves, and fruit peel and flesh the cork spots decreased. Cork spots increased as the P and K content of the leaves increased. Core data showed that cork spots decreased as the B and Mg content increased and the B × Mg interaction decreased. There was no relation between number of cork spots and the leaf and fruit content of Mn, Fe, Cu, Zn, or Al, despite significant effects of the treatments on these elements.