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Michigan State University researchers are testing various harvesting equipment on tart cherries that aren't amendable to traditional trunk shaking harvesters. This Korvan blueberry harvester, showing promise in preliminary tests, was able to harvest cherr

Michigan State University researchers are testing various harvesting equipment on tart cherries that aren’t amendable to traditional trunk shaking harvesters. This Korvan blueberry harvester, showing promise in preliminary tests, was able to harvest cherr

Adapting an over-the-row blueberry harvester for tart cherries has several advantages compared to existing mechanical harvesters that work by shaking the trunks of tart cherries, says a Michigan State University horticulturist. However, the technology would require a different tree training system from the traditional, widely-spaced, tart cherry trees.

Dr. Ron Perry, MSU horticulturist, sees potential with the over-the-row harvester for tart cherries after spending a season working with a Korvan 7420 blueberry harvester. "We tried it out and I was very impressed," he said, adding that overall, the test went surprisingly well. "In no case was the canopy of the tart cherry trees too large for the harvester."

The harvester uses plastic finger-like rods to gently loosen the fruit from the tree and has a five by eight foot tunnel opening to pass over the bush or tree.

Over-the-row harvesting of tart cherries, though new to the United States, has been done in Eastern Europe for several years. Perry mentioned that growers in Poland and Serbia have been using the technology on their tart cherries that are grown on smaller, more bush-form trees than U.S. growers.

Korvan, originally based in Lynden, Washington, made a variety of different harvesters, from grapes to olives to blueberries, before selling their line to International Corporation.

Perry and his MSU colleagues are working to improve mechanical harvesting of tart cherries. Existing equipment uses a trunk-type shaker, catching the fruit with canvas frames underneath the tree. The process requires several workers to conduct the harvest and there must be enough space between trees to maneuver the canvas catch frames.

"An over-the-row harvester would allow us to get away from the trunk shaker," he said, explaining that trunk shaking reduces the life of the tree and can exacerbate problems with trunk-boring insects.

He points out several advantages that the over-the-row technology has:

• Less physical damage to the tree

• More efficient (fewer workers needed)

• Continuous harvesting (no stop and start around each tree)

• Faster harvest

• Allows for nighttime harvest when temperatures are cooler

Genetic potential

The field experiments with the Korvan harvester were conducted in the test plot of MSU’s aggressive cherry breeding program headed by Dr. Amy Iezzoni. Some 35 seedling selections that would fit the tunnel opening were identified from Iezzoni’s test plot of new cherry plant material. The selections had not been pruned or trained since planting, and no growth regulators were used on the fruit to encourage abscission. A Montmorency tree was pruned so it would fit the Korvan tunnel opening.

Although the Montmorency variety is Michigan’s mainstay tart cherry, Perry believes that it’s a matter of time before new varieties and rootstocks for the sweet and tart charry industry come out of MSU’s breeding program.

He pointed out that Iezzoni is using a diverse pool of genetic material, with some that have dwarfing traits that would not be big enough for trunk shaking equipment. Trunk shakers require considerable room between trees and vertical space from the ground up to maneuver the catch frames underneath and around the trees. "But the new genetic material would be adaptable to over-the-row technology," he said.

The Korvan harvester would require a new type of training system for tart cherry growers. "You’d plant the trees like blueberry bushes—down a row—and grow them in a multi-stem bush-form similar to the Spanish Bush training system," he said. "I do think it has potential for the future."

Perry is working to receive grant funding to continue field research this summer to fine-tune the harvester specifications for tart cherries

Trials at MSU have also included using a modified drum berry harvester developed by U.S. Department of Agriculture’s Don Peterson of Kearneysville, West Virginia.