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Robert C. Ebel, Jacqueline K. Burns, Kelly T. Morgan, and Fritz Roka

harvesting systems use a canopy shaker composed of a vertical axis with 12 sets of free-floating tines 2 m long that radiate out from the vertical axis (Ebel et al., 2009; Whitney and Hedden, 1973 ). The 12 sets of tines span 3.5 m from the lowest to the

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Sergio Castro-Garcia, Uriel A. Rosa, Christopher J. Gliever, David Smith, Jacqueline K. Burns, William H. Krueger, Louise Ferguson, and Kitren Glozer

fruit damage was still at unacceptable levels. To reduce olive damage, the canopy harvester was modified by the incorporation of padding material to rods and other surfaces likely to contact fruit. Fig. 1. Experimental olive canopy shaker used during

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Richard S. Buker*, Jackie K. Burns, and Fritz M. Roka

Continuous canopy shakers (CCS) were developed in the late 90's and have been used to commercially harvest citrus in Florida. A viable mechanical harvester in Florida must be able to selectively remove mature `Valencia' fruit. A study was conducted to evaluate the effect of operating conditions on mature and immature fruit removal during the 2003 harvest season. The study was conducted in the southern flat woods and northern ridge areas. The study treatments were completely random and replicated four times. The CCS treatments were 145, 215, 230, and 245 cycles per minute (cpm) and a hand picked control. The harvest occurred on 17 and 19 June at the southern and northern sites, respectively. Mature fruit removal linearly increased from 95.7% to 97.9% between 145 and 245 cpm, respectively. Varying the operating ranges significantly influenced mature fruit removal in the southern flat woods site. The trees at the southern site were taller (>4m), and had a larger crop load. At the northern ridge site where trees were smaller, varying the CCS operating ranges did not significantly influence mature fruit removal. Immature fruit removal was influenced by the operating ranges. Immature fruit removal was increased at least 22% over hand picked controls. The results were interpreted to indicate the frequency of CCS is dependent on tree size. The initial selectivity of the CCS was not equal to hand picking.

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J.R. Schupp, T. Auxt Baugher, S.S. Miller, R.M. Harsh, and K.M. Lesser

-frequency electrodynamic limb shakers ( Diezma and Rosa, 2005 , Glozer and Hasey, 2006 ), high-pressure water streams ( Byers, 1990 ), and rotating rope curtains ( Baugher et al., 1991 ). As growers modify training systems for automation by maintaining narrow canopy

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Robert C. Ebel, Jacqueline K. Burns, and Kelly T. Morgan

-behind canopy shaker without a catch frame (Model 3210; OXBO International). Fruit on the ground were collected and weighed. Preharvest fruit drop, removal, and glean percentage were calculated as described in the 2006 procedure. In the second trial, fruit were

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Juan Carlos Melgar, Jill M. Dunlop, and James P. Syvertsen

; Roka, 2004 ). The shaking and visible injuries that citrus trees may experience during MH with trunk or canopy shakers are considered major impediments to the widespread adoption of MH ( Li and Syvertsen, 2005 ; Zekri and Syvertsen, 2008 ). However

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Kuo-Tan Li and James P. Syvertsen

1 To whom reprint requests should be addressed; e-mail ktli@ufl.edu . We thank John Crum from FMC Corp. for use of the trunk shaker and data acquisition systems. Fernando Alferez, Baylis Carnes, Jill Dunlop, Igor Kostenyuk, Luis Pozo, Ana Redondo

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Jacqueline K. Burns, Richard S. Buker III, and Fritz M. Roka

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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Kuo-Tan Li, Jim Syvertsen, and Jacqueline Burns

The shedding of leaves, branches, flowers, and young fruit; scuffing of bark; and exposed roots that are caused by trunk or canopy shakers during harvest appears to be unavoidable, but generally does not reduce long-term yields. Nonetheless, such visible injuries have limited the widespread adoption of mechanical harvesting in Florida's citrus industry. We determined if such physical injuries caused by a properly operated trunk shaker resulted in any physiological injures or any consequent decline in vigor and productivity of well-managed, healthy citrus trees. We continuously monitored various physiological indexes in mature `Hamlin' and `Valencia' orange trees annually harvested by hand or by a linear-type trunk shaker with various shaking durations. Trunk shaking did not reduce return bloom, fruit set, young fruit growth, or canopy and root growth. There was a correlation between the seasonal timing of a simulated bark injury and recovery from the injury. Although some root exposure was frequently observed during trunk shaking, leaf water relations and fine root growth were unaffected. There was no difference in leaf dry weight per area and leaf nitrogen among treatments. Mechanical and hand harvesting in late season `Valencia' during full bloom removed similar amounts of flowers. However, immature fruit were removed by trunk shaking when `Valencia' were harvested after mid-May, and the number of young fruit removal increased with shaking duration and fruit size. The loss of young fruit for the next crop remains a major problem of mechanical harvesting in late harvest `Valencia'.

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Jacqueline K. Burns*, Richard S. Buker, and Fritz M. Roka

A study was initiated in `Hamlin' orange to determine if a selective citrus abscission material, 5-chloro-3-methyl-4-nitro-1H-pyrazole (CMNP), could improve mature fruit removal and recovery when used with mechanical harvesters. A trunk shaker and continuous-moving canopy shaker equipped with catch-frames were used at the flatwoods and ridge growing regions in Florida. Both trials were conducted during the first 2 weeks of Dec. 2003. Plots were constructed as randomized complete blocks containing four replicates for each treatment. Each replicate contained five trees at the ridge site or four trees at the flatwoods site. CMNP was applied using a commercial airblast sprayer at 0, 125, 250 and 500 mg·L-1 at a rate of 2,800 L·ha-1 4 days before scheduled harvest. The trunk shaker was operated for either 7 seconds or 2 seconds/tree, whereas the canopy shaker was operated at either 260 cpm or 140 cpm/tree. The data show that the correct time was selected for harvest. Over a 50% reduction in FDF was achieved with the 250 and 500 mg·L-1 treatments, while post-application fruit drop was less than 1.5%. The greatest benefit of abscission agent use was seen when the mechanical harvesters were operated at the least aggressive setting (2 seconds or 140 cpm), where increases in % fruit removal and recovery were over 20% higher than the controls. At the most aggressive settings, numeric increases in % fruit removal and recoveries were measured, but these changes were not statistically significant. The results demonstrated that statistically similar % fruit removal and recoveries could be achieved using less aggressive harvester settings with abscission agent use when compared with most aggressive settings using no abscission agent.