Establishment on the Application Times of Foliage Spray with CaCl2 for Water Core Reduction in Apple

The objective of this study was to clear up the application times of CaCl₂ solution for reduction of water core, one of the physiological fruit disorders found in 'Hongro' apples. Recently, abnormally high temperatures in summer have induced more water core in fruit. Therefore, we introduced foliage spray with CaCl₂to improve physicochemical properties that can decrease water core incidence. We performed field experiments at 9 orchards in Chungcheongbukdo from the end of June to July in 2012. We tested 6-year-old+ 'Hongro' trees at orchard elevations ranging from 126~306 m. The pH levels of soil  ranged from 4.1~7.7 and Ca²⁺ soil content ranges were 0.9~9.5 (standard contents of Ca²⁺ are 5~6). The CaCl₂ solution diluted by 0.3% was sprayed one to five times on orchard foliage. Water core incidences were indexed 0~9. The incidences of water core on the control orchards ranged 1.35~2.20 and those on CaCl₂ treated orchards  ranged  0.95~1.75. Fruit weights between treatments in each orchard were not different. The CaCl₂ treated orchards had 1~5 times reduced water core by 28.6%, 13.0%, 19.2%, 35.5%, and 54.8%, respectively. In the highest orchard, the one-time treatment of CaCl₂was effective, however in lower orchards four treatments were more significant for water core decrease. The results showed the possibility that foliage spray of CaCl₂ solution over four times reduces water core by improving the physicochemical properties in the trees.