Field evaluation of targeted shake-and-catch harvesting technologies for fresh market apple

Apple is the most economically important agricultural crop in Washington State. In 2018, Washington State produced ∼3.3 billion kg of apple, accounting for approximately 63% of U.S. production. Fresh-market apple is currently harvested manually, requiring large numbers seasonal semi-skilled workers for a small harvest window. To overcome the increasing challenges of uncertain labor availability and raising labor costs, a promising mechanical harvesting system, using a targeted shake-and-catch approach, is under development at Washington State University. This study evaluated the system by analyzing its fruit harvest efficiency and fruit quality with three shaking methods, i.e., continuous non-linear, continuous linear, and intermittent linear shaking, on up to six apple cultivars trained to formal tree architectures. Results showed that intermittent linear shaking achieved 90% fruit removal efficiency for 'Scifresh' cultivar, while continuous linear shaking achieved only 63% removal efficiency for 'Gala'. This study also compared three vibratory systems: A hand-held system, a hydraulically driven system, and a semi-automated hydraulic system. The semi-automated system achieved the highest fruit removal efficiency (90%), followed by the hand-held (87%) and hydraulic (84%) systems, mainly due to the different shaking methods employed. However, the differences were statistically insignificant. Fruit catching efficiency varied among the harvesting systems, with the hand-held system achieving the highest efficiency (97%), followed by the hydraulic (91%) and semi-automated (88%) systems. Among the three tested technologies, the prototype semi-automated system achieved the highest level of mechanization, as well as high fruit removal efficiency and the best fruit quality. Because the semi-automated system did not include an auto-positioning function, positioning its shaker head took about eight times longer (∼103 s) than the actual shaking time (∼13 s), which suggests that a fully automated system is desirable to further increase productivity. This study showed that the shake-and-catch approach has great potential for practical adoption in harvesting of fresh-market apple and therefore can have a positive economic impact on the U.S. apple industry.