Can growers harvest cherries by machine?

THE GORGE — Last week, Columbia Gorge News covered a pear-centric session at the Washington State Tree Fruit Association’s (WSTFA’s) annual meeting, where growers talked about tight margins and marketers emphasized the lack of young buyers. Now, it’s time for cherries.

Held in Wenatchee from Dec. 8-10, farmers had the opportunity to receive training, learn about the latest technology and crowdsource solutions to pressing challenges at WSTFA’s event, also called the Northwest Hort Expo. On day two, Matthew Whiting, a professor of tree fruit horticulture at Washington State University, unpacked 22 years of research that interrogated one question: Can a machine harvest cherries without sacrificing quality?

In short, yes.

“These rudimentary and albeit prototype harvest systems are demonstrating the potential to dramatically improve harvest efficiency,” Whiting said.

After multiple iterations, the latest machine looks like a weed whacker. But rather than a rotating blade on one end, there’s an arm that hooks around branches and vibrates at a frequency optimized to make cherries fall. Called a shaker, it’s accompanied by a retractable net intended to catch fruit before it hits the ground.

While the industry has been grappling with labor shortages for years, Whiting’s presentation came at a particularly apt time. Increasingly dependent on foreign workers, at least one local grower started picking this year without half of his normal workforce, as first reported by Columbia Gorge News. Much of his crew travels up the West Coast following harvests, but large-scale immigration raids targeted farms in California just before Oregon’s season began.

Not an automated system, the shaker requires a pair of hands to function; however, it works at speeds much faster than someone picking cherries individually, mitigating the demand for labor. In one trial, a human picked Coral Champagne and Skeena cherries at a rate of 1.3 and 1.6 pounds per minute, respectively. The shaker, by contrast, harvested 3.9 pounds of Coral Champagne cherries in one minute, and seven pounds of Skeena.

Based on those numbers, it would take one person working eight-hour shifts with the shaker 21 days to harvest 10 tons of Coral Champagne cherries and 12 days for Skeena cherries, whereas picking the same quantity of both varieties by hand would stretch for more than a month, Whiting calculated. Each method also produced a similar amount of bruising, pitting and punctures.

“Combined, we saw about 10% in the hand-harvested fruit and 13.5% from the shake and catch system, which was not statistically significant,” said Whiting. “In other words, if we had done this trial 100 times, it would come up the same.”

One caveat, though, was the proportion of cherries left behind because they were dropped or, more likely, because they never came off the tree. The shaker only captured 68-85% of the total possible yield, but Whiting was confident the difference could be “virtually eliminated” with strategic pruning, as weaker branches aren’t great conduits for vibrations.

Still, some in the audience were skeptical. Because the machine is fairly small and maneuverable, Whiting stressed there’s little need to change canopy architecture or the space between rows. Buyers also tend to perceive cherries with green stems as being higher quality, but the shaker removes all stems during the harvest process.

“The long-term storage of cherries without stems is better than cherries with stems,” Whiting said. “All of our consumer studies over the years have underscored the same point: There’s a willingness, and in many cases, we’ve demonstrated a preference from consumers to purchase cherries that don’t have stems.”