DEFOLIATION, BENDING AND TIP PRUNING OF APPLE UNDER TROPICAL CONDITIONS

In 1979 these treatments were compared separately and combined in a factorial experiment on mature trees. Each of the eight treatment combinations were applied to whole trees and replicated three times. Three random 10-shoot samples at high, middle and low positions in each tree were recorded. The experiment was carried out in both the wet and dry seasons.

Of the three treatments, defoliation had the greatest effect on bud burst, and thus subsequent growth and cropping (fig. 1). Ninety five percent bud burst occurred within four weeks of defoliation in the wet season. There was slow bud burst rising to only 80% after 20 weeks in the dry season. Without defoliation similar levels of bud burst were not attained until 12 and 20 weeks in the wet and dry seasons respectively.

Branch bending also increased bud burst but the effect was mainly in the dry season alone and in combination with defoliation (fig. 1). In the wet season bending had a slight effect and only in the absence of defoliation.

Pruning alone had a small effect in the wet season in the absence of defoliation (fig. 2). In the dry season it had no effect alone but an additive effect to defoliation.

Defoliation is the most effective stimulus to bud burst. If water supply is not limiting defoliation induces adequate bud burst. Under dry season conditions both bending and pruning cause an additional stimulation which justifies their use if irrigation is not possible.

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