Influence of pre- and post-harvest treatments on bitter pit of Granny Smith apples in the Goulburn Valley

Abstract

Methods of controlling storage pit of Granny Smith apples were studied in the Goulburn Valley from 1960 to 1966. Foliar sprays of calcium nitrate reduced pit but boron sprays did not. Most efficient control was achieved with three or more sprays applied between December and March. Residual effects from such sprays were not observed the next season. Foliar sprays of calcium nitrate increased the concentration of calcium in spur leaves but not in fruit tissues. Dipping unsprayed fruit after harvest in solutions of calcium chloride or calcium nitrate, or wrapping fruit in paper sheets impregnated with calcium salts, gave negative or inconsistent results. Such treatments did not usually alter the concentrations or amounts of calcium, magnesium, or potassium in fruit tissues. The concentration of calcium in all fruit parts declined as fruit size (dry weight) increased. Since pit severity also increased with increasing fruit size, the calcium status of the fruit, fruit size, and pit incidence were closely related. The concentration of calcium in mesocarp + endocarp showed the highest negative correlation with pit severity of any of the fruit parts, and this tissue was therefore the best indicator of the calcium status and pit susceptibility of the fruit. It is concluded that pit is not due to an inbalance between calcium, magnesium, and potassium in the fruit but that it is merely the syndrome of calcium deficiency in the apple fruit. No differences were found in flavour characteristics between pitted and sound fruit.