Improving efficacy of abscission sprays for mechanical harvesting of oranges

Muhammad Farooq, Masoud Salyani, Jodie D. Whitney

Abstract


Two studies were conducted in commercial orange groves in central and south Florida with the overall objective of reducing the cost of application while increasing the efficacy of the abscission chemical sprays. In the first study to find optimum airflow rate, the fan speed of an air-blast (Titan) tower sprayer was varied from 1600 to 2200 rpm to achieve different airflow rates. In the second study, a drift retardant adjuvant (In- Place) was used in the tank mix with and without a surfactant adjuvant at two liquid flow rates to enhance the efficacy of low volume applications with a Curtec tower sprayer. In both studies, the spray mixture contained 5-chloro-3-methyl-4-nitro-1-Hpyrazole (Release), an experimental abscission material, and a fluorescent tracer. Spray deposition was sampled at different canopy locations and quantified by fluorometry. Harvesting efficacy was quantified by measuring fruit detachment force (FDF), percent fruit drop (PFD) and percent fruit removal (PFR) by a trunk shaker. With the Titan sprayer, none of the spray treatments resulted in significantly different percent fruit removal than the unsprayed control. With the Curtec sprayer, the use of a drift retardant adjuvant was effective in reducing fruit detachment force. Percent fruit removal significantly increased with addition of a surfactant (Kinetic®). It appears that the economics and efficacy of the abscission chemical applications may be improved by using lower airflow rates and certain adjuvants.

Keywords


airflow; nozzle; 5-chloro-3-methyl-4-nitro-1-h-pyrazole; pyranine; fruit detachment force; trunk shaker; sprayer; adjuvant

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Proc. Fla. State Hort. Soc.     ISSN 0886-7283