Mechanical Pruning Becoming More Viable for Grape Producers

Researchers continue to look at how mechanical operations affect crops as labor costs continue to rise. Central Valley wine, table grape and raisin growers gathered in Fresno County to watch mechanical grape pruning machines in action.

UC Cooperative Extension Viticulture Advisor for Fresno County George Zhuang coordinated the demonstration that was a partnered effort between UCCE and Golden State Vintners. The field day demonstrated two different mechanical pruning machines on several varieties growing on different trellis systems.

The machines pruned established pinot grigio vines on classic California sprawl trellis’ and several young third-leaf varieties on a single high-wire and a modified California sprawl (low-wire) trellis. Zhuang noted he was also testing the affects of pruning such young vines.

Mechanical pruning research is nothing new. Zhuang said research into the practice started decades ago. “Mechanization, particularly mechanical pruning, is nothing new and has been around for 20 or 30 years,” he said. “Previously it didn’t take off because there was no real incentive.” With prodcution costs continuing to rise with minimum wage increases, that incentive is now there.

There are concerns with mechanical pruning like its negative affects on wine grape taste but Zhuang said those are the types of things that need to be tested with modern equipment and vines. “We need to revisit that whole theory because with today’s machines and technology we can make more precision prunings,” Zhuang said.

One of the lesser known benefits of the practice is trunk disease management. Zhuang said pruning can be significantly delayed with the machines. Ideally, pruning could be postponed until March after winter rains and when the plant begins to awaken and can heal faster. “The most ideal time for pruning is the day before bud-break but we cannot do that because of labor and logistics” Zhuang said. “With mechanical pruning you can get it as late as possible.”