The developer of a mechanical vine pruning machine brought to market in Australia about 30 years ago says U.S. growers may now be paying attention to the technology because of high labor costs associated with hand crews.

Fred Spagnolo, the Australian engineer who designed the Spagnolo pruning technology, says the technology has been commercially available in the United States for over a decade now. It is now being tested by University of California viticulture specialists on a variety of raisin grapes that shows promise for its labor-saving traits.

As labor costs in California escalate, growers are becoming more interested in cost-saving technology. The Sunpreme variety of raisin grapes, developed by the U.S. Department of Agriculture and released in about 2014, lends itself to more efficient pruning and harvesting.

The variety naturally dries on the vine, according to George Zhuang, a Cooperative Extension farm advisor who specializes in grapes in the Central Valley. Combined with an ability to mechanically box hedge the vines during the dormant season, Zhuang says this will be the first year the variety will experience fully mechanized management from bud break to harvest.

Selma grape grower John Chandler said the technology looks promising. Chandler now grows just wine grapes after pulling his dry on the vine raisin grapes last season because the cost of employing hand crews to cut canes ahead of harvest and perform other vine management tasks was too costly.

"It's encouraging to and good to see the UC introduce us to this technology," Chandler said at a field day demonstration.

University testing

Zhuang and his colleague, Matthew Fidelibus, a viticulture specialist with the UC Cooperative Extension, are studying the technology and its impacts on vines. Though the study has been ongoing for a few years now, a few minor setbacks unrelated to the grape variety itself will cause researchers to start over after replanting some vines inadvertently damaged by herbicides.

Zhuang said the box hedging of vines in January will begin the process to test mechanical pruning and harvesting of the variety.

Mechanical pruning in raisins was unheard of until recently, despite the availability of equipment that could do the job, Zhuang said. Now he hopes to demonstrate the capabilities of machines for growers and eventually steer them away from the expensive labor crews by showing significant cost benefits of a fully mechanized vineyard.

Fidelibus believes the Sunpreme variety shows promise with mechanical management, despite drawbacks in the variety that includes fragile fruit. This can lead to the potential of fruit loss during harvest when raisins fall to the ground.

Still, Fidelibus says mechanical harvesting may be the best way to handle the Sunpreme variety because of that fragile nature as too much manual handling by hand crews and processing could reduce fruit quality to unmarketable levels.

Machines

Spagnolo's machine and one made by the U.S. based company Vmech were demonstrated recently for growers at a field day hosted by the University of California. In both cases the machines made short order work of box pruning raisin grapes on a single-wire trellis. It is traditional for growers to prune vines during the dormant season with plenty of time before bud break to avoid issues, Fidelibus said.

In both cases, the machines either attach to a vineyard tractor or are pulled behind a tractor capable of operating between the vine rows.

Steve Roland with Vmech says the Missouri-made machine is being offered by direct sale to growers. Aside from box hedging the vines, Roland says attachments are available to shoot thin and perform other vineyard practices.

More information on the Vmech machine can be found at vmech.com. For the Spagnolo machine, visit spagnolo.com.au.

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