Preharvest fruit splitting (PFS) is a serious problem in Ellendales, especially in hot, humid climactical areas. In control unsprayed treatments PFS can vary from 14 to 30% of the final yield. Any treatment during the fullbloom (FE) period aimed at increasing fruit set (gibberellic acid (GA) sprays, girdling), increases PFS levels, ranging from 40 to 60% of the final yield. This relates to a significant shift (delay) in the normal fruit drop pattern as compared to untreated trees.
We have evaluated various approaches aimed at reducing PFS in Ellendales: potassium treatments, from 10 weeks pre-blossom to six weeks after full-bloom, however, increased PFS levels, possibly due to increasing the initial fruit set levels; flower thinning, both chemical and mechanical, marginally reduced PFS, without adversely affecting yield; post-November drop GA application, 2,4-D and girdling treatments, aimed at stimulation of rind growth (not quantified) increased yields significantly (P<0.05) without concurrent increases in PFS.
Cross pollinated trees, and resultant high seed content in the fruit, yielded fruit with thicker rinds, with little or no PFS. GA application at FE reduced fruit seed content and peel thickness and increased PFS.
Any treatment causing high initial fruit set increases PFS. Flower: flower and fruit: fruit competition should be reduced early during the fruit growth phase, without adversely affecting final yields.