A Four-year Study of Single Calcium Chloride and Growth Regulator Tree Sprays to Control Storage Breakdown of ‘Spartan’ Apples1

A single spray of 2.5 or 5% CaCl 2 applied 14 days before harvest significantly reduced breakdown of ‘Spartan’ apples ( Malus domestica Borkh.) in each of 4 consecutive years and caused no residual tree or crop damage. Indole-3-butyric acid (IBA) alone or in combination with CaCl 2 led to significant reductions in breakdown in only 1 of the 3 seasons in which it was tested. Ca applied in 1 season did not influence fruit Ca levels the next year. Both 2.5 and 5% CaCl 2 applied in 1973 significantly increased Ca in fruit peel, flesh and core tissues. Although IBA did not increase fruit Ca levels, a strong negative relationship between fruit Ca and breakdown susceptibility was evidenced by analyses in 3 crop years. Fruits located near the top of the trees were lower in flesh Ca than those from the bottom. This, plus inadequate spray coverage in the top of the tree canopies, led to poor control of breakdown in these fruits when the sprays were applied at lx, 3x or 6x concentration with an air-blast orchard sprayer using 3342, 1114, and 557 1 of water per hectare, respectively.