CENTER LEADER APPLE TREE RESTRUCTURING FOR IMPROVED YIELD DISTRIBUTION AND FRUIT QUALITY
Mature, 18-year-old, overgrown center leader ‘Granny Smith’ apple trees in a commercial property were restructured during the 1987 and 1988 dormant seasons into either palmette center leader or pyramid center leader forms. In the palmette center leader, pruning was restricted to removing the uppermost east- and west-facing (between row) fruiting scaffolds in 1987, with wood pruned from the middle fruiting scaffold and north-upper scaffold in 1988. In the pyramid center leader, the trees were subjectively pruned in stages over 2 years to reestablish the desired pyramid shape. Unmodified top-dominant trees were maintained as controls. The trial involved 10 blocks (five rows and two treatment replications per row) with four trees per treatment in which only the middle two trees were monitored. All trees in the trial were managed with renewal pruning methods in contrast to the containment pruning maintained on the remainder of the commercial property. 1) Highest quality spurs, as assessed by leaf areas, leaf dry weights, leaf numbers and fruit bud diameters were recorded in the restructured pyramid center leader trees, although the differences among treatments were small. 2) Within the renewal-pruned trees, no differences in total yield were detectable among treatments in the lower tree regions, but mean fruit size was highest from the palmette center leader canopy. Yields in the upper tree regions were 33% and 19% lower in the palmette and pyramid canopies, respectively. In both instances, however, mean fruit size and hence fruit size distribution was improved. 3) Total yield was 1.5 times higher in the renewal-pruned compared with the containment-pruned trees. When combined with the restructuring treatments, this pruning method resulted in 50% and 80% yield increases in the lower tree canopies, respectively, for the pyramid and palmette forms. 4) The upper : lower tree ratio for total yield over the 3 years following restructuring was 1.8:1.0 in the control trees and 1.1:1.0 in the restructured canopies. The major restructuring treatments, combined with renewal-pruning methods, improved fruit distribution within the tree, improved harvesting efficiency, and significantly improved yield and fruit size. The restructuring strategies used were simple, did not promote unduly excessive vegetative growth and enhanced the quality of spurs in lower canopy regions.
Hirst, Peter M., Stuart Tustin, D., Cashmore, Wendy M., Warrington, Ian J., Jill Stanley, C., Julian, John F. and Catley, J. (1992). CENTER LEADER APPLE TREE RESTRUCTURING FOR IMPROVED YIELD DISTRIBUTION AND FRUIT QUALITY. Acta Hortic. 322, 267-268