Regulating pre-harvest fruit drop and the duration of the harvest season of grapefruit with 2,4-D and GA

Abstract

SummaryThe effects of 2,4-D, GA and their combinations on pre-harvest fruit drop and the duration of the harvest season of Marsh Seedless grapefruit were evaluated. Pre-harvest fruit drop increased as the season advanced and had two main peaks: in August and in December, about 10 and 14 months respectively after fruit setting. Total accumulated fruit drop amounted to 34% during the ten months after treatment; of this amount 6% occurred in the first five months and 28% in the latter five months. When applied in May all treatments reduced fruit drop to various degrees, the combined 2,4-D+GA sprays being most effective. The combined sprays were also most effective in delaying rind aging which was related to rind pigments and resistance to puncture, thus extending the harvest season by up to ten months without any unfavourable effects on juice quality. However, a second 2,4-D spray in July had no effect on fruit drop or harvest extension. None of the treatments used affected the alternate cropping pattern of ...