GROWTH AND CROPPING OF APPLE TREES AS INFLUENCED BY GROWTH REGULATORS AND PRUNING METHODS

H. Link
Vigorous growth and crop load of the trees are considered to be fundamental factors of alternate bearing in modern orchards. Successful fruitgrowing requires an effective control of both these phenomena.

To regulate tree vigour growth regulators and certain pruning treatments were applied to experiment trees. Both, growth regulator and pruning treatments showed very similar results in respect to tree architecture. Regulated growth of the trees seemed to be a function of the number of laterals per unit branch length: if there were only a few laterals, vigorous growth could be expected and vice versa. The application of growth regulators normally led to many weak laterals on branches easier than pruning, because shoot growth was reduced instantly by such a treatment, so that all the laterals could be spared at pruning. In comparison, shoots of untreated trees grew more vigorously, particularly when there were only a few laterals on the branches, so that the field workers were tempted to cut off these unwanted shoots and worsen so the situation.

Alternate bearing as an effect of a too heavy crop load could not be restricted satisfactorily by conventional fruit thinning with NAAm in some apple cultivars. So adjuvants for NAAm were investigated, in order to increase the thinning action. Another attempt was made by a combined spray with Alar and Ethrel. Normally it gave good repeat bloom, but sometimes there was a severe fruit drop to be seen in these plots. So, when results of some consecutive years were compared, total crop by an additional Alar/ Ethrel treatment often was not higher than with a single NAAm thinning spray. As for the effect of a special summer-pruning method on alternate bearing, results were at least as favourable as in the growth regulator plots.

Link, H. (1986). GROWTH AND CROPPING OF APPLE TREES AS INFLUENCED BY GROWTH REGULATORS AND PRUNING METHODS. Acta Hortic. 179, 207-214
DOI: 10.17660/ActaHortic.1986.179.22
https://doi.org/10.17660/ActaHortic.1986.179.22

Acta Horticulturae