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Du Chen, a visiting doctoral student at Washington State University in Prosser, tests a cherry with a digital force gauge. This testing is done to determine the force required to separate the fruit from the stem.

Du Chen, a visiting doctoral student at Washington State University in Prosser, tests a cherry with a digital force gauge. This testing is done to determine the force required to separate the fruit from the stem.

Washington State University

In order to remain competitive in the global market, sweet cherry producers, retailers, and researchers have banded together to drive innovation along the entire ­production chain.   

This molecules-to-market project, called “a total systems approach to developing a sustainable, stem-free sweet cherry production, processing, and marketing system,” will wrap up its second year of research in August. The four-year project is funded by a U.S. Department of Agriculture Specialty Crop Research Initiative grant. Participating collaborators include the lead institution, Washington State University, along with Oregon State University, Michigan State University, the University of California, and Picker Technologies, of Seattle, Washington.

The project’s long-term goal is to develop a sustainable, highly efficient sweet cherry production, processing, and marketing system with effective research and outreach programs addressing the total system. This project addresses the needs, identified by stakeholders, to improve harvest labor efficiency and improve the fruit’s overall consumer appeal. Our research and outreach programs incorporate the entire value chain of sweet cherry production, processing, and marketing. The overall goal is to create a model total systems approach for effectively and efficiently adopting innovation in the sweet cherry industry.

Why innovate?

The annual sweet cherry harvest is one of the most labor-intensive of all agricultural endeavors. Harvest costs for sweet cherries are highest among tree fruits, accounting for approximately 60 percent of the cost of production, largely due to the amount of fruit per tree, large unwieldy tree architectures, and the lack of mechanical harvest options. The general harvest process for sweet cherry fruit has not evolved in over a century—laborers carry and place their ladder in the tree, climb to access fruit, pick the fruit at its stem (pedicel), place the fruit into a bag secured over their shoulders with straps, then climb down and dump the fruit into either a lug or bin. It is estimated that sweet cherry harvest requires approximately two-to-threefold more labor hours per unit of land than other temperate tree fruit for reasons listed above. In the Pacific Northwest, the cherry industry faces imminent labor shortages due to a variety of factors, including immigration reform, increased demand for harvest labor, and competition for laborers from other industries. This insufficient supply of harvest labor has significant and potentially ruinous consequences for the sweet cherry industry.

If new harvest technologies can be developed, worker safety will also improve. The perils of ladder-intensive harvest are well documented and underscore the desperate need for innovative harvest technologies. The adoption of a mechanical and/or mechanical-assist harvest system for sweet cherries has the potential to revolutionize the sweet cherry industry. Tests have shown that the USDA-ARS prototype harvester dramatically reduces labor without negative effects on fruit quality, but produces a stem-free cherry product. Preliminary market research has shown consumer acceptance of stem-free cherries.

However, the potential for stem-free cherries has not been realized for lack of an integrated system from field to table. The hope is within the four years of this research project, an integrated production, processing, and marketing system will be available for ­industry to adopt.

Progress/research findings

Objective 1: Develop a high efficiency, productive, angled fruit wall orchard system.

In 2010, four new orchards were planted (2 in Oregon, 2 in Washington) as research/demonstration sites for the angled UFO (Upright Fruiting Offshoot) architecture. Another UFO orchard was planted with a collaborator in Tasmania, Australia, to provide a site for counter-seasonal research. Two additional orchards are set to be planted in Washington and Oregon this spring. A “how to” video is also in the works and should be available in June 2011.

Objective 2: Establish the genetic basis for sweet cherry abscission.

Sweet cherry cultivars and breeding populations were phenotyped for pedicel retention force and fruit traits including weight, size, stem length, firmness, acidity and sweetness in 2009 and 2010. Significant differences in pedicel retention force were observed among cultivars and between years as well as between cultivars and years. This significant genotypic variation for pedicel retention force suggests that it will be relatively easy to breed for low pedicel retention force.

Work was also done to test the established model of abscission in sweet cherry. In year one, cherry genes homologous to abscission-related genes from other species were identified, and samples were collected to identify genetic networks associated with pedicel-fruit abscission in sweet cherry.

Objective 3: Improve labor efficiency and safety by developing mechanical and/or mechanical-assist harvest ­technologies.

The USDA mechanical harvester and the shake-and-catch mechanical-assist harvester were both field tested for efficiency and impact on harvest efficiency and fruit quality. Field demonstrations of harvest technologies were conducted. Researchers also analyzed the minimum single impact or vibration excitation force applied to a cherry tree to create a detachment force on a cherry stem. This will help provide necessary information for developing a new stem-free cherry ­harvester.

A functional mockup of Picker Technologies’s transport tube was also constructed and is ready for evaluation. Picker Technologies also conducted “time to pick” studies in order to understand the economics of a fruit handling system, and made progress in modifying ­existing in-field cooling technologies for sweet cherries.

Work was also done on developing a yield monitoring system for mechanical assist or fully mechanized sweet cherry harvest. Two major activities were focused on in this area of research, one focused on developing high resolution mapping capabilities to collect base data on cherry orchards, the other focused on measuring worker harvest efficiency.

Objective 4: Extend shelf life/ ­consumer appeal of sweet cherries.

Three different experiments were conducted in 2010 to preliminarily assess the effect of packaging, temperature, and cherry variety on the shelf life and quality of fresh sweet stem-on and stem-free cherries. Some of the preliminary findings were that shelf life of the stem-free and stem-on cherries was notably affected by the type of package, surrounding temperature, and cherry variety. In addition, a prototype bio-based container reduced the cherry weight loss by about 5, 8, and 10 percent after one, two, and three weeks of storage. A packaging survey was also developed and designed to collect critical information from cherry growers, packers, retailers, and consumers. The acceptance of plastics made from natural resources as alternative packaging materials to the ­petroleum-based ones is explored in the survey.

Objective 5: Develop markets for stem-free sweet cherries and determine optimum shelf life.

Consumer evaluations of stemmed and stem-free cherries were conducted. Consumers used a 7-point hedonic scale for evaluation of overall appearance, size, shape, color, overall taste/texture acceptance, acceptance of juiciness, firmness and flavor. Consumers were also asked their willingness to purchase the cherries based on a set price per pound. Results were that significant differences were found in the overall appearance acceptance and acceptance of size of the stemmed vs. the stem-free cherries. The stemmed cherries had a higher mean overall appearance acceptance and size acceptance compared to the stem-free cherries. However, no differences in flavor, taste, or texture attributes were found between the stemmed and stem-free cherries.

Objective 6: Analyze system profitability, market potential, and develop economic models for outreach and adoption.

New technologies are often assumed to be too expensive, unproven, or only affordable for large-scale growers. Economic analysis has begun to evaluate potential for new technology to generate a profit for all growers. Much of 2010 was allocated to to the development of the ­AgFinance software program and constructing a new Web site for AgTools. This information will be discussed with growers in the coming year to determine the ­differences in costs between farm sizes.

You can keep up to date with our research project at http://sweetcherryresearch.wsu.edu. Our Web site contains news, research highlights, photos, videos, and much more. You can also sign up to receive our monthly e-newsletter on our Web site. For more information on the project, please e-mail tracie.arnold@wsu.edu.

Tracie Arnold is Project Coordinator/Communications Specialist at Washington State University, Irrigated ­Agriculture Research and Extension Center, Prosser.