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A portable, handheld, mechanical shaking device was developed and its effects on fruit detachment in rabbiteye bluebbery (Vaccinium ashei Reade) and southern highbush blueberry (hybrids of mostly Vaccinium corymbosum L. and Vaccinium darrowi Camp.) were evaluated. The instrument facilitated effective detachment of fruit within a branch, especially in rabbiteye blueberry (greater than 75%). Approximately 3 to 4 seconds of shaking was sufficient to detach the majority of the fruit. Differences in the extent of fruit detachment were observed across the genotypes, especially among southern highbush blueberry genotypes. The majority of fruit detachment in rabbiteye blueberry and most of the southern highbush blueberry genotypes occurred at the point of attachment of the pedicel to the berry, although a significant portion detached with the stem intact, resulting in stemmy fruit. Although only a small proportion of the detached fruit was immature in the rabbiteye blueberry genotypes, up to 23% of the detached fruit was immature in the southern highbush blueberry genotypes. Application of the abscission agents methyl jasmonate (MeJa; 20 mm) and ethephon (1000 mg·L−1) reduced the time required for fruit detachment on mechanical shaking by up to 5-fold. Together, these data indicate that the mechanical shaking device developed here is an effective tool for studying fruit detachment in blueberry. This instrument has potential applications in blueberry research programs evaluating fruit production. It can be used in breeding programs to aid in the selection of genotypes with fruit detachment characteristics that are potentially better suited for mechanical harvesting, and also in programs involving the screening and evaluation of abscission agents in blueberry.

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Field and growth chamber experiments, and grower trials, were conducted to determine the effects of GA3 sprays on yield and fruit quality of rabbiteye blueberry (Vaccinium ashei Reade) in northern Florida and southern Georgia. Multiple GA3 sprays at various stages of flower development increased fruit set and yield in field experiments (Florida) and grower trials (Georgia) when compared to controls. Nonpollinated rabbiteye flowers sprayed with GA3 had greater percent fruit set and delayed fruit development compared to hand pollination. Percent fruit set and average fruit weight were reduced at 21C night temperature when compared to 10C night temperature for both hand-pollinated and GA3-treated fruit. Overall, yields were increased by multiple applications of GA3 during bloom, but average fruit size was reduced and the fruit development period was lengthened.