Blueberry (Vaccinium spp.) production has increased greatly over the last decade, especially in the southeastern United States. It is currently valued at over $780 million in the United States [U.S. Department of Agriculture (USDA), 2012]. Sustaining the profitability of the blueberry industry requires a better understanding and the mitigation of problems associated with its production. Harvesting is generally one of the most expensive and labor-intensive aspects of blueberry production, especially when fruit are hand-picked. Mechanical harvesting can greatly reduce the costs associated with harvesting. Owing to the growing interest in the use of mechanical harvesting in blueberry, especially for fruit intended for the fresh market, there are considerable research efforts underway to enhance the efficiency of this process. In fact, a current area of focus of several blueberry breeding programs is the development of genotypes better suited for mechanical harvesting (NeSmith, 2009; Jim Olmstead, Steve Stringer, and Jim Ballington, personal communications). An additional area of research is the development of abscission agents that can facilitate fruit detachment and enhance the efficiency of mechanical harvesting (Malladi et al., 2012; Takeda et al., 2008; van Dalfsen and Gaye, 1999).
Better knowledge of fruit detachment properties is valuable in blueberry breeding because it is closely associated with suitability of a genotype for mechanical harvesting. Performing trials using commercial mechanical harvesters may be the most conclusive method to determine the suitability of a genotype for mechanical harvesting. However, such evaluations cannot be performed during the selection process in breeding programs as a result of factors such as the scale at which the plants are grown and the cost associated with such trials for multiple genotypes. Hence, much of the current evaluation of fruit detachment characteristics of genotypes during breeding and selection is performed through hand-harvesting. Evaluation of potential abscission agents to determine their effect on fruit detachment is essential to develop harvest aids that can enhance the efficiency of mechanical harvesting (Burns, 2002; Burns et al., 2005; Malladi et al., 2012). Such screening may not always be feasible using commercial-scale mechanical harvesters. A portable, handheld instrument that can allow for the mechanical shaking of a branch may provide an effective alternative and can greatly aid in blueberry breeding and abscission agent research efforts. The main objectives of this study were to develop a portable, handheld mechanical shaker and to evaluate its effects on fruit detachment in blueberry. To achieve the objectives, a reciprocating saw was modified to enable controlled mechanical shaking of blueberry branches. This instrument was evaluated across multiple rabbiteye and southern highbush blueberry genotypes. Additionally, mechanical shaking studies were performed using this instrument after treatment with abscission agents.
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