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  • Author or Editor: Jacqueline K. Burns x
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An abscission agent [5-chloro-3-methyl-4-nitro-1H-pyrazole (CMNP)] was applied to `Hamlin' and `Valencia' orange (Citrus sinensis) trees at concentrations ranging from 0 to 500 ppm in a volume of 300 gal/acre. Four days after application, fruit were mechanically harvested with either a trunk shake-and-catch or a continuous canopy shake-and-catch system commercially used in Florida. Harvesting conditions were varied by limiting the actual trunk shake time of the trunk shaker to 2, 4, or 7 seconds, or by altering the ground speed of the canopy shaker (1.0, 1.5, or 2.0 mph). In general, increasing duration of shake and the application of CMNP increased percent mature fruit removal and decreased the amount of fruit remaining in the tree. Increasing CMNP concentration decreased fruit detachment force but increased post-spray fruit drop. Comparison of short duration shake times in CMNP-applied trees with trees harvested at longer durations either sprayed or not sprayed with CMNP indicated no significant difference in percent mature fruit removal. The results demonstrate that CMNP application increases harvesting capacity of trunk and canopy shakers by reducing time necessary to harvest each tree while maintaining high percent mature fruit removal.

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Fruit of 11 citrus cultivars were evaluated for their response to the experimental abscission material metsulfuron-methyl at 2 mg·L-1 (ppm) active ingredient as an aid to mechanical or hand harvest. Cultivars evaluated included `Ambersweet', `Glen Navel', `Hamlin', and `Valencia' oranges [Citrus sinensis (L.) Osb.], `Robinson' tangerine (Clementine × Orlando, C. reticulata Blanco), `Sunburst' tangerine [`Robinson' × `Osceola', C. reticulata × (C. paradisi Macf. × C. reticulata)], `Murcott' and `Temple' tangor (C. reticulata × C. sinensis), `Orlando' tangelo (C. reticulata × C. paradisi), `Ray Ruby', and `Marsh' grapefruit (C. paradisi). Six of the 11 cultivars were effectively loosened by sprays of metsulfuron-methyl (`Hamlin', `Valencia', `Orlando', `Murcott', `Temple', and `Ray Ruby'). Addition of an adjuvant (Kinetic, 0.125%) was necessary for abscission activity in fruit and leaves. Trees sprayed with metsulfuron-methyl in combination with an adjuvant had higher percent cumulative fruit drop, higher internal ethylene, and lower fruit detachment forces (FDF) than trees sprayed with metsulfuron-methyl alone. `Sunburst' tangerine responded poorly to the abscission material in the presence or absence of Kinetic. Leaf loss was greatest in trees sprayed with metsulfuron-methyl and adjuvant, intermediate in trees sprayed with metsulfuron-methyl alone, and least in control trees. Twig dieback was observed in trees of `Valencia' orange and `Marsh' grapefruit sprayed with metsulfuron-methyl. The peel of some cultivars had irregular coloration and developed pitted areas after harvest. Although metsulfuron-methyl is an effective abscission agent for mature citrus fruit, further work is needed to more accurately define conditions for its safe and dependable use.

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Table olives (Olea europaea) traditionally are hand harvested when green in color and before physiological maturity is attained. Hand harvesting accounts for the grower's main production costs. Several mechanical harvesting methods have been previously tested. However, tree configuration and fruit injury are major constraints to the adoption of mechanical harvesting. In prior work with a canopy shaker, promising results were attained after critical machine components were reconfigured. In this study, stereo video analysis based on two high-speed cameras operating during the harvesting process were used to identify the sources of fruit damage due to canopy-harvester interaction. Damage was subjectively evaluated after harvest. Fruit mechanically harvested had 35% more bruising and three times as many fruit with broken skin as that of hand-harvested fruit. The main source of fruit damaged in the canopy was the strike-impact of fruit by harvester rods. Implementation of softer padding materials were effective in mitigating fruit injury caused by the impact of rods and hard surfaces. Canopy acceleration was correlated with fruit damage, thus restricting improvements needed for fruit removal efficiency through increased tine frequency.

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