Evaluation of abscission chemicals in various combinations for loosening Valencia oranges during re-greening

SummaryAll chemicals, tested alone or in combinations with Ethrel, had little effect until late in the Valencia season after January. Despite less force required to detach the fruit, the overall percentage of fruit removed declined due to natural fruit re-tightening until March, when true abscission increased with natural senescence. The combination of Ethrel+Pik-off+Harvade caused the lowest fruit detachment force, the highest fruit removal, the most true abscission and had the most consistent effects throughout the season. The next best treatments were Ethrel+Pik-off, and Ethrel alone. Ethylene production from the chemicals was highest for the triple combinations and for Ethrel and its double combinations. Natural fruit detachment had two main periods of weak fruit attachment: December-January, the physiological fruit drop period, and February- March, the early fruit senescence phase.