Some growers using the open-gable dried-on-the-vine (DOV) raisin production system have been disappointed to find their yields falling short of those reported in research trials conducted at the University of California Kearney Agricultural Center, Parlier

The DOV systems there, typically, produce about 4 tons of raisins per acre. That compares to the 3.5 to 3.75 tons-per- acre yields reported by many DOV growers, notes Matthew Fidelibus, a UC Cooperative Extension viticulture specialist, based at the Kearney facility.

He’s in the middle of a two-year study to see if he can find the reason for this difference. Fidelibus is conducting field trials to study the effects of various canopy management systems on grape production. Also, he’s visiting DOV vineyards using open gable trellises to compare their features with those of the open gable trellises used in the Kearney research vineyards.

 

 

He’s waiting until the end of trials this season to draw any firm conclusions. But, Fidelibus suspects the variation in production levels reflects differences in the way growers and researchers manage exposure of the vines to sunlight.

The Kearney DOV system was developed in the 1990s by L. Peter Christensen. It features an open-gable design with a Y-shaped trellis, which can support cordon or head-trained vines.

“It’s important to provide renewal shoots with the best possible exposure to sunlight in order to optimize bud fruitfulness and minimize bud necrosis.” Fidelibus says. Christensen intended this exposure to be achieved through the use of rake wires, which could be used to gather renewal shoots toward the center of the trellis where a foliage catch wire was mounted.

To save the cost of wires and metal stakes, he’s observed that many growers don’t include rake wires or a center foliage catch wire in their open gable DOV systems. These omissions could reduce exposure of the renewal shoots to sunlight and, thus, account for some of the yield reductions growers are reporting, he notes.

 

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Some other growers separate renewal from fruiting shoots by pruning the vines so that all the fruiting canes are trained to grow on one side of the vine and all the spurs on the other.

“This way, every other space between the vines is either all fruiting canes or all spurs,” Fidelibus explains. “The idea is that, since there are no fruiting canes next to the spurs, the renewal shoots will receive more sunlight.”