Nearly 48,000 acres or just over 28 percent of the state’s total raisin acreage was picked mechanically, according to a recent report by the U.S. Department of Agriculture.

The overhead trellis management system was used on 13,695 bearing acres in 2015, accounting for 8 percent of the total raisin-type grape acreage.

Fresno and Madera County growers have 48 and 40 percent of the overhead trellis acreage in the state, respectively. Kern County growers have 10 percent of the overhead trellis acreage. 

Other mechanical harvest systems include continuous tray at 19 percent of the acreage and south side with less than 1 percent of the raisin-type grape acreage. Open gable accounted for less than 1 percent of the total raisin acreage.

Fresno County had the most raisin acreage subjected to mechanical harvesting methods. Like the state numbers, only 28 percent of the county’s total raisin acreage, or over 33,700 acres, were harvested mechanically.

Kern and Madera County growers harvest 21 and 40 percent of their raisin-type grape acreage by mechanical means, respectively.  

By variety, Thompson Seedless grape acreage with mechanical harvesting is 35,041 or 23 percent of the total raisin-type grape acreage. Seventy-two percent of the Fiesta grape acreage is harvested mechanically and 56 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.

Funding for the raisin-type grape acreage report was provided by the Raisin Administrative Committee.