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  • Author or Editor: Louise Ferguson x
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As one of the oldest continuously produced tree crops in the world, it is ironic that table olive (Olea europaea) production has benefitted from few technological innovations, including harvesting. Two harvesting technologies, trunk shaking and canopy contact, have been identified. In a 2013 trial, a prototype canopy contact harvester successfully harvested 92% of a 5.3-ton/acre mechanically pruned crop, vs. 81% for a 12.8-ton/acre hand-pruned control crop in a 19-year-old, 13 × 26-ft grove, spaced at 139 trees/acre and adapted for mechanical harvesting with 6 years of mechanical topping and hedging. About 85% of the hand-pruned olives were cannable vs. 86% of the mechanically pruned olives. Over the 6 years of mechanical pruning, the mechanically pruned trees averaged an annual 4.2 tons/acre vs. 5.3 tons/acre with hand-pruned trees. Again in 2013, this same canopy contact harvester achieved 81% final harvester efficiency with a 5.8-ton/acre crop in a 12-year-old, 12 × 18-ft, 202-tree/acre, mechanically pruned hedgerow grove vs. 80% efficiency for a 5.17-ton/acre crop with hand-pruned hedgerow trees. Similarly, no significant differences in the percentage of cannable olives, fruit size distribution, or value per ton was produced by the pruning treatments. In this trial in which both hand and mechanical pruning were used to produce a hedgerow, the hand-pruned trees averaged 3.7 tons/acre vs. 4.3 tons/acre for mechanically pruned trees. In a commercial trial in 2012, the trunk-shaking harvester achieved 77% average harvester efficiency in a 40-acre, 180-tree/acre grove, with a 4-ton/acre crop prepared with both hand and mechanical pruning. These ongoing trials indicate that adapting groves with mechanical pruning does not decrease average annual yields and can produce table olive groves that can be mechanically harvested at a cost and speed that is competitive with hand harvesting.

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There are two ways salinity can damage citrus: direct injury due to specific ions, and osmotic effects. Specific ion toxicities are due to accumulation of sodium, chloride, and/or boron in the tissue to damaging levels. The damage is visible as foliar chlorosis and necrosis and, if severe enough, will affect orchard productivity. These ion accumulations occur in two ways. The first, more controllable and less frequent method, is direct foliar uptake. Avoiding irrigation methods that wet the foliage can easily eliminate this form of specific ion damage. The second way specific ion toxicity can occur is via root uptake. Certain varieties or rootstocks are better able to exclude the uptake and translocation of these potentially damaging ions to the shoot and are more tolerant of salinity. The effect of specific ions, singly and in combination, on plant nutrient status can also be considered a specific ion effect. The second way salinity damages citrus is osmotic effects. Osmotic effects are caused not by specific ions but by the total concentration of salt in the soil solution produced by the combination of soil salinity, irrigation water quality, and fertilization. Most plants have a threshold concentration value above which yields decline. The arid climates that produce high quality fresh citrus fruit are also the climates that exacerbate the salt concentration in soil solution that produces the osmotic effects. Osmotic effects can be slow, subtle, and often indistinguishable from water stress. With the exception of periodic leaching, it is difficult to control osmotic effects and the cumulative effects on woody plants are not easily mitigated. This review summarizes recent research for both forms of salinity damage: specific ion toxicity and osmotic effects.

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Most fig (Ficus carica) cultivars have potentially two crops; fruit from the first crop are called brebas. This crop is commercially important in some Mediterranean area cultivars. The second or main crop, called figs, is the commercially important crop for most fig cultivars. Due to labor cost increases, harvest of the breba crop, with its low production and lower quality fruit, has become economically unviable in some cultivars. Unharvested brebas are potential sites for fungal pathogens and they attract insects. Spring ethephon applications of 250 to 500 ppm applied before full leaf expansion, when the largest fruit are about 1.5 to 2 cm in diameter reduced the breba crop load (≈92%) without adverse side effects. The use of early fall ethephon applications of 500 ppm also resulted in breba crop load reductions (≈30%), but with significantly lower efficacy than spring treatments. These fall and/or spring ethephon treatments did not affect the percentage of vegetative budbreak, breba weight, breba soluble solids concentration, fig crop load, fig weight, or ethephon residues. Thus, early spring ethephon application at 300 ppm (0.22–0.36 kg·ha−1), when breba fruit and leaves are just starting to develop and figs are not present, was a safe, effective and inexpensive way (about $16 per hectare) to reduce the breba crop. Currently, ethephon is included in the federal IR-4 program, and residue studies are ongoing as a protocol for future registration.

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The `Manzanillo' olive (Olea europaea L.) is widely grown in California, because olive processors prefer its uniform size and quality for their canned product. Although it is self-compatible, 10% of a planting should be committed to a pollinizer cultivar to promote optimal production of seeded `Manzanillo' fruit and minimal occurrence of worthless parthenocarpic “shotberries.” As fruits of pollinizer cultivars are of substantially less value and more difficult to manage within a `Manzanillo' planting, less commitment of land for pollination purposes would be desirable. Here we show that topical applications of supplemental olive pollen can be a feasible alternative to commitment of land to olive pollinizer cultivars within a `Manzanillo' planting.

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Developing mechanical harvesting is the most effective, and most difficult, factor in improving horticultural crop profitability. It requires simultaneous incremental changes by multiple entities; engineers, horticulturists, food scientists, economists, local extension personnel, the commercial harvester industry, growers, and displaced laborers and their management. There is a narrow annual testing window. The initial research by engineers and horticulturists focuses on developing effective removal technologies and can be applied or basic. When funding is local, the research is generally applied and is usually an adaptation of existing technology. With national funding, the research is basic or investigates novel technologies. Both are conducted first on model systems or individual plants. Properly executed, both types can be published, but publication is difficult if engineering parameters are changed during the trials. Evaluation of developed removal technologies requires cross-disciplinary teams to evaluate the effects on the final marketable product quality and long-term plant health. Publications can be produced on testing technology or effects on marketable product quality or plant health. An industry education program with field days, industry publications and websites, and annual presentations should frequently report progress. Finally, a prototype should be demonstrated to show the economic feasibility of a mobile platform with catching technology. The research team then expands to include the harvester industry and grower cooperators. Orchard adaptations to increase harvester efficiency are incorporated at this point. Usually by this time all research is applied and the funding local. If results demonstrate economic feasibility, the technology should now segue to the commercial harvester industry as university laboratories mostly lack the capacity to generate truly commercial harvesters. Publications could be delayed to avoid premature disclosure to make patents achievable and to facilitate cooperation between university researchers and commercial fabricators.

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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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