|Takeda, Fumiomi - Fumi|
Submitted to: HortTechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/6/2007
Publication Date: 12/19/2007
Citation: Takeda, F., Krewer, G., Andrews, E., Peterson, D.L., Mullinix, J. 2007. Assessment of V45 blueberry harvester on rabbiteye blueberry and southern highbush blueberry pruned to v-shaped canopy. HortTechnology. 18(1):130-138. Interpretive Summary: Southern highbush blueberries in Georgia are hand harvested for fresh market. In contrast, rabbiteye blueberries are machine harvested for fresh market but their shelf life is short and quality is much lower than hand harvested fruit. Hand harvesting of southern highbush blueberries costs $0.45 to $0.70 per pound and needs as much as 550 worker-hours per acre. Harvesting costs for rabbiteye blueberry are slightly less. Labor costs are projected to rise while fruit prices are expected to drop as the blueberry industry expands in Georgia and finding enough hand pickers during the peak harvest season may become difficult. Compared to hand harvested fruit, fruit harvested by commercial over-the-row, mechanical blueberry harvesters is less firm, subject to internal browning, and does not cold store well. Previous studies in Michigan conducted by USDA scientists showed that the internal quality and firmness of northern highbush blueberries harvested by their experimental USDA blueberry harvester (V45) was as good as hand harvested fruit. Based on these results, a grower in Georgia tried to use a V-45 to harvest rabbiteye and southern highbush blueberries that were minimally pruned and it performed badly. The V45 harvester caused severe limb breakage and even pulled entire plants out of the ground. In this study, we determined the effect of pruning on the productivity and machine harvestability of rabbiteye and southern highbush blueberry plants. We found that winter pruning of large rabbiteye blueberry plants reduced yield. Pruned plants may take more than three seasons to become as productive as unpruned plants. In the smaller, fast-growing southern highbush blueberry, summer pruning stimulated new cane production from the plant crown and flower buds developed on new shoots so that yield was not reduced. High quality rabbiteye blueberry fruit was harvested with the V45 harvester if a “V” was created by removing upright and overarching canes from the plant center. The V45 harvester easily passed through the bush, split the bush left and right, and engaged the canes through the shaking mechanism. Internal quality of V45 harvested fruit was as good as hand harvested fruit. The V45 harvester removed too many green fruit and too many fruit with stems on the southern highbush blueberry. Improved mechanical harvesting system for blueberries in Georgia is critical considering the rising cost of hand harvesting and a potential labor shortage. Long term studies are needed to develop pruning strategies that allow use of the V45 harvester without the negative effects on harvest efficiency.
Technical Abstract: Studies were performed to evaluate the V-45 blueberry harvester on specially pruned rabbiteye and southern highbush blueberry. Two- to 2.5-m-tall, six-year-old rabbiteye plants were winter-pruned in February 2004 and 2005 and one- to 1.5-m-tall, three-year-old southern highbush blueberry plants were summer pruned in June 2004 or dormant pruned in February 2005. Pruning consisted of cutting all canes that were growing vertically or over-arching in the center of the plant. Pruning removed an estimated 30 percent of canopy and opened the middle, resulting in a “V” shaped plant. Yield of pruned ‘Brightwell’ blueberry was lower compared to unpruned plants in both 2004 and 2005, but pruning had no effect on yield in ‘Powderblue’ blueberry. In southern highbush cultivars, postharvest summer pruning in 2004 did not reduce their 2005 yield, but winter-pruning in February 2005 did when compared to unpruned plants. Observed cane damage by V45 on pruned blueberry plants was minimal. V45-harvested blueberries had internal damage much lower than that from sway harvester and approached that of hand harvested samples. Further refinements are needed to reduce fruit defects, such as immature green and stemmed blue fruit. Also, the pruning practices must be modified and mechanized to facilitate mechanical harvesting.