An over-the-row raspberry harvester is tested for harvesting cider apples
Cider apple growing overall requires fewer inputs than growing dessert fruit because superficial blemishes don’t detract from the quality of apples that go into cider.
But cider apples are typically small—the size of a tennis ball or smaller—which makes them expensive to harvest.
“It takes a long time to fill a bin,” said Drew Zimmerman, cider maker and former owner of Tulip Valley Vineyard and Orchard in Mount Vernon. “Really, the only way that this can practically be done is by mechanical harvesting. In order for the grower to make money, he’s going to have to take advantage of all the mechanical help and use as little labor as possible.”
Dr. Carol Miles, who heads the tree fruit program at Washington State University in Mount Vernon, is exploring if raspberry harvesters could be used for harvesting apples. There’s a significant raspberry industry in the area, and the harvesters sit idle in the fall after the raspberry season is over. The harvesters are roadworthy, but have a maximum speed of about five or six miles per hour. Miles envisions that they would be transported between raspberry fields and orchards on flatbed trailers.
She is conducting replicated trials with a cider variety called Brown Snout in the WSU orchard, comparing hand and machine harvest. Ideally, for mechanical harvest, the trees should be on dwarf rootstocks and trained to a trellis to form a low fruiting wall. The harvester has rotating beater bars that vibrate the branches so the fruit falls out of the trees and onto a conveyor belt, which carries the fruit up to a bin at the top of the machine.
The beater bars are weighted. For apple harvesting, they are set at the maximum weight and velocity, which is a simple adjustment that can be made in the field.
One of the difficulties Miles has encountered is that the conveyor belt’s cups are too small for some of the larger apples, so they sometimes get jammed. According to the manufacturer of the harvester, it would be a relatively simple process to change the belt to one with cups big enough for apples.
Results from the 2011 harvest indicate that hand harvest required eight times more labor hours per acre than machine harvest. That translates to a difference in labor costs of $105 per acre, assuming an hourly wage of $10 to $12 per hour plus taxes and benefits. The time spent mechanical harvesting includes hand labor for cleaning up the fruit left on the trees and picking up groundfalls.
Although mechanical harvesting was much faster, it resulted in a 10 percent yield loss. Miles reported that the amount of groundfalls and fruit left on the tree could be reduced by some changes in tree training, such as removal of limbs too low for the machine to pick up and development of shorter fruit-bearing limbs at right angles to the row. Also, tying upright branches more loosely to the trellis would allow enough motion for the fruit to be shaken from the branches. Machine harvesting caused very little damage to limbs and spurs.
Fruit for cider is harvested tree ripe, and Miles said use of growth regulators to manage harvest might be worth future study.
All the mechanically harvested fruit was bruised and some cut or split, but Miles said that is not a problem when the apples are used for cider. Although damaged fruit could be susceptible to rot if stored before pressing, in the study no increased rot was seen in fruit that was cold-stored for two weeks. There was no difference in the quality of the juice from hand- and mechanically harvested apples or from storage.
The experiment is being repeated this fall.