Application of Abscission Sprays for Mechanical Harvesting of Hamlin Orange

Abstract

The success of technologies for mechanical harvesting of Florida citrus, in part, depends on the efficacy of abscission sprays that are applied to reduce fruit detachment force. The objective of this research was to determine the effects of sprayer type, sprayer airflow rate, and spray volume rate on deposition and abscission efficacy of CMN-Pyrazole, in mechanical harvesting of oranges. Two experiments were conducted in February 2001, using air-blast and air-curtain tower sprayers. The sprayers were equipped with an axial-flow fan/ hydraulic nozzles and cross-flow fans/ rotary atomizers, respectively. Both sprayers discharged the spray uniformly, along the sprayer tower height, to 5.5–6.5 m high ‘Hamlin’ orange trees. Spray mixtures, containing CMN-Pyrazole, adjuvant Kinetic, and a fluorescent tracer (Pyranine 10G), were applied at 1,170 and 2,340 L/ha. Leaf samples were collected from different canopy locations and spray deposition was quantified by fluorometry. Four days after the applications, fruit detachment force was measured at different canopy heights and dropped fruit was counted. The trees were shaken with a trunk shaker and percentage of fruit removal was determined. Spray deposition and the relationship between deposition and mechanical harvesting parameters were determined for different modes of spray application.