Mechanical harvesting of raisins saves on labor costs

With labor being a major component of raisin production, a growing number of raisin producers are shifting to mechanical harvest.

Total raisin grape acreage harvested by mechanical means now totals 31,483—representing just more than 16 percent of the state's overall raisin acreage—according to the U.S. Department of Agriculture National Agricultural Statistics Service.

NASS released last week results of its latest survey of mechanical raisin harvesting, based on results from the 2013 Grape Acreage Report.

For the past seven years, the agency explained, the survey conducted in order to compile the report has included an additional question intended to gather information on raisin-type acreage that is harvested mechanically. In addition, farmers were asked to update acreage by variety and year planted.

The report released last week summarized data for raisin-type grapes grown using three mechanical harvest methods:

• Overhead trellis—Grapes are dried directly on the vine, forming a canopy over the rows. It allows the mechanical grape harvester to get underneath and gather the dried fruit.
• South-side trellis—In an east-west row orientation vineyard, an angled cross-arm is added to each trellis stake to support two wires on which fruiting canes are tied. The southern exposure of the fruit facilitates drying. The raisins may be harvested mechanically with a south-side harvester.
• Continuous tray—Grapes are mechanically harvested and laid out on a continuous (rather than individual) thin sheet of paper, where they dry in the sun for two or three weeks.

The overhead trellis management system was used on 14,604 bearing acres in 2013, accounting for 8 percent of the total raisin-type grape acreage.

Fresno and Madera county growers have 41 percent and 36 percent of the overhead trellis acreage in the state. Kern County growers have 21 percent of the overhead trellis acreage.

Other mechanical harvest systems include continuous tray at 8.5 percent of the acreage and south-side with less than 1/2 of 1 percent of the raisin-type grape acreage.

Fresno County has the most acreage with mechanical harvesting, at 19,121, which represented 14 percent of the Fresno County raisin-type grape acreage. Kern and Madera county growers harvest 25 percent and 27 percent of their raisin-type grape acreage by mechanical means, respectively.

By variety, Thompson seedless grape acreage with mechanical harvesting was 21,344, or 12 percent of the total raisin-type grape acreage. Sixty-two percent of the Fiesta grape acreage was harvested mechanically and 46 percent of the Selma Pete acreage was harvested mechanically.

Most California raisins are produced by sun drying after placing the bunches on paper trays on terraces between vine rows. The overhead trellis system has led to increased production of dried-on-the-vine raisins, increased machine harvesting and decreased hand labor use, according to NASS.