Dec 2, 2011
Tree fruit growers still looking for a mechanical harvester

Michael Glenn, director of USDA’s Appalachian Fruit Research Station in Kearneysville, W.Va., can list all kinds of technological innovations that have aided tree fruit growers in the last 50 years: lasers and GPS for more precise tree planting; trellising for improved light interception, yields and efficiency; pneumatic pruners, hydrolifts and mobile platforms to aid human workers; more efficient sprayers that also protect workers; packing-line sensors that sort fruit; computer-aided disease prediction; mechanical thinners, etc.

As of yet, Glenn cannot add a mechanical harvester to that list. Mechanical harvesters have made inroads in crops like blueberries, tart cherries and grapes, but growers of fresh-market apples, sweet cherries, peaches and other tree fruit are still waiting for a readily available machine that, unaided by the human hand or eye, can remove a piece of fruit from a tree without bruising it.


Serious mechanization of commodity crop harvests began about 150 years ago, but labor-intensive specialty crops like fruits and vegetables were “industrialization’s rejects,” said Vincent Bryan Jr., a founder of Picker Technologies in Mercer Island, Wash.

Mechanization has come unevenly to fruits and vegetables. It’s a patchwork of crops and seasons, some served by shakers and other machines but most served by a horde of unskilled, low-wage workers from other countries, Bryan said.

“We like to joke that progress in the tree fruit industry has come a long way – we’re still picking apples and peaches with a bag and a ladder, the same way it was done a hundred years ago,” wrote Katie Ellis, an Extension educator at Penn State University, in an article posted on Penn State Extension’s website Oct. 25.

The need for progress accelerated in 1964, when the U.S. government scrapped the Bracero Program, the country’s agricultural guest-worker program at the time. Bracero’s demise dried up the labor pool for U.S. fruit and vegetable growers, which spurred USDA’s Agricultural Research Service (ARS) and various land-grant universities to study mechanization as a way to replace those lost laborers, said Donald Peterson, a retired research agricultural engineer.

When ARS hired Peterson in 1970, he was one of 10 engineers working on six projects related to fruit harvesting. Sixteen more engineers from land-grant universities were working in conjunction with ARS, he said.

At the time, processing crops like prunes, tart cherries, brambles and, to a limited extent, peaches in California were being mechanically harvested, but fresh-market tree fruit posed greater difficulties. Non-uniform ripening was one problem; fruit damage caused during detachment, fall through the canopy or collection was another, Peterson said.

In 1979, Peterson earned his Ph.D. from Michigan State University and transferred to ARS’ Appalachian Fruit Research Station in West Virginia. His original assignment was to study mechanized apple harvesting, but President Jimmy Carter threw him a curveball. It was about 1980 when the Carter administration – under pressure from United Farm Workers and other labor groups – announced that USDA would no longer fund research of mechanized harvesting. The University of California and other land-grant institutions stopped funding mechanization research at about the same time, for similar reasons, Peterson said.

That was part of the shift of mechanization research from the public sector to the private sector. Advances continued, but the overall pace of development in the produce industry slowed down, said Jack King, manager of California Farm Bureau’s national affairs division.

Within the next dozen years, ARS shut down every mechanical fruit harvest research project it was working on – except Peterson’s projects. He was the only ag engineer left, and his responsibilities ended up stretching far beyond apples.

Peterson thinks the powers that ran ARS were glad to retain a researcher who studied fruit mechanization – they just wanted him to stay under the political radar. And there was still plenty of interest in fruit mechanization from the industry. Peterson spent the intervening years studying fruit harvests all over the country – from blueberries in Michigan to brambles and cherries in Oregon to citrus in Florida.

Glenn, director of the Appalachian Fruit Research Station, listed some of Peterson’s – and the station’s – contributions to the fruit industry: Peterson developed the spiked-drum/shake/catch harvesting system used in many variations for blueberries, blackberries and citrus; Peterson, Stephen Miller and Glenn developed a variation of the spike drum for use as a flower and fruit thinner in apples and peaches; Fumi Takeda and Peterson developed the rotatable cross-arm trellis system for mechanical harvesting of blackberries; Peterson improved over-the-row, contained sprayer technology.

Peterson also experimented with a machine that picked apples from trees planted to a Y trellis, but the design never got traction because the problem of bruising the apples couldn’t be solved without making the tree canopy so thin that resulting yields weren’t worth the effort, Glenn said.

Meanwhile, the farm labor situation only got worse – to the point where, in the early 2000s, the federal government began to revive its support for mechanizing fruit harvests. Peterson and other ARS personnel were able to take advantage of that renewed interest.

“My last year or two with ARS was amazing,” Peterson said.
Despite that excitement, Peterson wasn’t replaced when he retired at the end of 2005. That was disappointing, he said. Government funding is hard to come by, but the fruit industry needs it if it’s going to find ways to replace human workers.

Tart cherries

Tart cherries were harvested by hand until the late 1960s, when growers concerned about labor shortages started using mechanical shakers, catching frames and de-stemmers, said Jim Nugent, a retired Michigan State University (MSU) horticulturist.

Over the years, mechanization completely altered the way tart cherries were harvested, changing everything from tree shape to processing techniques. The new technologies were driven by a combination of MSU engineers, private industry and growers tinkering in their garages, Nugent said.

They had certain problems to overcome. Limb shakers and early trunk shakers were notorious for damaging trees, leaving them more susceptible to pests that would further injure them. As a result, tree life was shortened significantly, he said.

When tart cherry growers started using harvesting machines, they were using them on trees that had been trained for hand harvest. The short trunks and low-hanging limbs were convenient for human pickers, but didn’t leave much room for a mechanized trunk shaker covered by an inclined catching frame. It became obvious that the structure of the tree needed to adapt to the equipment. Modern tart cherry trees now have longer trunks and higher branches, giving the shakers plenty of room. Combine that with better technology and better management techniques, and the average life of a tart cherry orchard is back to what it was in the hand-harvest era, Nugent said.

Migrant farm workers are still vital to the tart cherry industry, but the number needed is much smaller than it was 50 years ago, he said.

Sweet cherries

Shaking and catching would cause too much bruising on fresh-market sweet cherries, which need to be handled with care.
During his tenure with ARS, Peterson helped design a mechanical harvester for fresh-market sweet cherries. The harvester was not commercialized, but the design influenced Matt Whiting, a fruit physiologist at Washington State University.

With help from manufacturers and a USDA grant, Whiting is currently testing a prototype sweet cherry harvester. He hopes to have something commercially available within a few years.
If the sweet cherry is to be harvested mechanically, a narrow tree canopy is essential, Whiting said. A three-dimensional canopy doesn’t allow easy enough access to the tree’s interior.
So, in conjunction with the harvester, Whiting has been developing the Upright Fruiting Offshoots system, a two-dimensional growing system that meshes well with mechanization. UFO growers have already started mechanizing tasks like thinning and pruning, he said.

California grapes

Mechanization has made significant progress in California’s grape industries in the last few decades, especially in wine and raisins, said California Farm Bureau’s Jack King.

Mechanization has helped halve the raisin industry’s labor requirements. A decade ago, raisin growers needed about 50,000 workers during harvest. Now, they need about 25,000, he said.

King described one of the ways mechanization has eased labor requirements for raisin growers: Machines remove the grapes from the vine; other machines lay continuous paper trays on the ground for the grapes to dry on. Traditionally, human workers would lay their own small paper trays on the ground, cut grape clusters from the vine and set them on the trays by hand.

In California’s San Joaquin Valley, where grape prices are low, wine grapes are mechanically harvested and sometimes mechanically pruned, said Roger Duncan, a University of California Cooperative Extension adviser.

In the “premier” wine-growing regions of the state, where they can afford the labor, most things are still done by hand, Duncan said.

Renewed activity

In the last decade or so, the tree fruit industry has played a more active role in its quest for mechanized harvesters and other technological breakthroughs. Growers and researchers in Washington state developed the National Tree Fruit Technology Roadmap, an effort to boost the use of technology in the industry that grew to include other states.

In 2009, Jim McFerson, manager of the Washington Tree Fruit Research Commission (WTFRC), listed some of the projects affiliated with the roadmap: Oregon and Pennsylvania researchers were working with mobile platforms for pruning and harvest and with machines to thin fruit. Carnegie Mellon University, which works with robotics in many industries, was working on several problem-solving robots. Olin College was developing a robotic hand.

On top of all that, WTFRC invested hundreds of thousands of dollars to back the research efforts of Vision Robotics in San Diego. According to the company’s website, Vision Robotics is developing the Tree Fruit Scout, a machine that scans an apple tree with special cameras and picks the fruit with a series of long, reticulating arms. The company also is working on a robotic grape pruner.

Many of these efforts were aided by the 2008 Farm Bill, which boosted funding for specialty crops research.

The future

According to Ellis, the Penn State Extension educator, advances in specialty crop innovations have been gaining strength for years, whether factory-made machinery off a production line or improvements welded from odds and ends in a grower’s workshop.

U.S. agriculture has a rich history of small-scale innovators continually finding ways to do things better. Advances have been made, and will continue to be made, but it’s going to be tough to replace the human hand and eye, King said.

If the tree fruit industry is going to come up with a machine that completely replaces human harvesters, it will only occur when plant characteristics and machine designs are integrated into a compatible system. That will require engineers, breeders and horticulturalists to work together, Peterson said.

By Matt Milkovich, Managing Editor

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