Calcium sprays for control of bitter pit and other disorders in apples

Abstract

Calcium nitrate sprays were applied to 'Cox's Orange' apples over four different periods between fruit set and harvest.Four sprays applied early, from 8 October to 2 December, gave no control of bitter pit. With the other three periods (II days, 27 days, and 64 days pre-harvest) there was good control of pit. The relative values of these three later spraying periods for pit control were difficult to assess, but the 64-day period gave slightly less pit in one season. The highest levels of fruit calcium were with the 27-day pre-harvest period.Over 64 days pre-harvest, 6 sprays of 0.6% calcium nitrate doubled the total calcium in apples, whereas in unsprayed apples total calcium remained practically constant. Over this period the apples gained in weight fourfold, thereby reducing the percentage of calcium in ,prayed apples to one-half, and in unsprayed apples to near one-quarter.Calcium sprays reduced internal breakdown in 'Cox's Orange' and 'Red Delicious' apples. Colour development on 'Red Delicious' apples was retarded by calcium nitrate, but not by calcium chloride sprays.Apples which were protected from spray gained no benefit from four calcium nitrate sprays applied to the rest of the tree.