Total acreage harvested by mechanical means was 45,548, just over 30 percent of the State’s total raisin-type grape acreage, according to the Pacific Region Office of USDA’s National Agricultural Statistics Service. The Overhead Trellis Management System was used on 13,385 bearing acres in 2017, accounting for 8.9 percent of the total raisin-type grape acreage. Fresno and Madera County growers have 52 and 40 percent of the Overhead Trellis acreage in the State, respectively. Kern County growers have 6 percent of the Overhead Trellis acreage. Other mechanical harvest systems include Continuous Tray at 20 percent of the raisin acreage, South Side with 0.4 percent and Open Gable with about 0.9 percent of the raisin-type grape acreage.
Although Fresno County has the most acreage with mechanical harvesting, at 33,313, that acreage only represents 30 percent of the Fresno County raisin-type grape acreage. Kern and Madera County growers harvest 18 and 42 percent of their raisin-type grape acreage by mechanical means, respectively.
By variety, Thompson Seedless grape acreage with mechanical harvesting is 32,703 or 25 percent of the total raisin-type grape acreage. Seventy percent of the Fiesta grape acreage is harvested mechanically and 63 percent of the Selma Pete acreage is harvested mechanically.
Most California raisins are produced by sun drying after placing 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.