ISHS Acta Horticulturae 448: III International Symposium on Mineral Nutrition of Deciduous Fruit Trees
CONTROL OF BITTER PIT IN APPLE AND INTERNAL BREAKDOWN IN PLUM USING AN ORGANICALLY COMPLEXED CALCIUM CARRIER (CALCIMAX) |
| Authors: | J. Wooldridge, M.E. Joubert, W.A.G. Kotzé |
| Keywords: | boron, calcium, calcium nitrate, fruit quality, potassium, leaf scorch, russet, bitter-pit, apple, plum |
| Abstract:
Calcium nitrate sprays are routinely used by South African apple growers for the control of bitter pit. However, calcium nitrate causes leaf scorch and is not effective against internal breakdown in plum. An alternative calcium carrier (Calcimax) was evaluated in Western Cape orchards. A spray programme involving 0.45 % Calcimax sprayed at 10 to 14 day intervals from 6 December to just before harvest controled bitter pit in ‘Golden Delicious’, ‘Starking’ and ‘Granny Smith’ as effectively as conventional spray programmes containing calcium nitrate, but with lower levels of leaf scorch. Lenticel spot in ‘Granny Smith’ and russet in ‘Golden Delicious’ were also reduced. In ‘Celebration’ plum, internal breakdown was reduced relative to controls by a programme involving six 0.25 % Calcimax sprays applied at 14-day intervals commencing on 7 December. Sprays with Potmax (the potassium derivative of the carrier used in Calcimax) did not exacerbate internal breakdown. Neither Calcimax nor Potmax caused leaf scorch in plum. | |
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