California raisin grape growers continue their steady adoption of mechanical harvesting methods, according to USDA National Agricultural Statistics Service (NASS) reports.
Total acreage harvested by mechanical means in 2019 was 44,091, nearly 30% of the state’s total raisin-type grape acreage, according to the NASS Pacific Region Office. This number is up from just more than 16% six years ago.
The most popular mechanical harvest system was continuous tray, in which 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 system accounted for 19% of the acreage.
The second most popular method was the overhead trellis management system, in which grapes are dried directly on the vine (DOV), forming a canopy over the rows, allowing the mechanical grape harvester to get underneath and gather the dried fruit. It was used on 13,031 bearing acres, accounting for 9% of the total raisin-type grape acreage.
The open gable system was the third most popular, with about 1.2% of the acreage. In it, trellis wires are connected between rows of v-shaped supports. The V shape lets in additional sunlight and traps the heat, which greatly improves ripening and drying. Raisins are harvested mechanically with a harvester that has been modified to place the raisins in bins instead of gondolas.
The least popular mechanical harvest system was south side, in which vineyards are planted with an east-west row orientation. 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 then be harvested mechanically with a south side harvester. The system accounted for just 0.4% of the raisin-type grape acreage.
By variety, ‘Thompson Seedless’ grape acreage with mechanical harvesting is 30,922 or 25% of the total ‘Thompson Seedless’ acreage. Newer varieties are much more likely to be harvested mechanically. Nearly half of the ‘Fiesta’ grape acreage is harvested mechanically, and 67% of the ‘Selma Pete’ acreage is 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 DOV raisins, increased machine harvesting, and decreased hand labor use.