Borrowing from European designs
Gary Wilson of Wilson Ag in Shafter, Calif., has been working with mechanical pruning for nearly 20 years and agrees the approach not only helps manage costs but diseases as well.
Machine pruning was pioneered in Italy and Australia, where labor traditionally has been in short supply. Wilson began building his own machines shortly after hearing about innovations in those countries.
He now mechanically prunes all his own winegrape acreage in Kern County and commercially machine prunes for outside growers.
In the central San Joaquin Valley, Wilson says the mechanical pruning system typically is simpler than on the Central or North coasts.
He runs three different custom machine pruners that create a hedge-like box canopy. Except for Thompson seedless, Wilson hedge prunes all varietals.
With Thompsons, he prefers to skirt them to compensate for a lack of fruitfulness in the first buds.
Wilson Ag’s machines, which use a combination of rotary blades and sickle bars to create a box around the trellis, work best on simpler, single-wire trellis systems, he says. But machines are available that can accommodate more complicated crossarm and canopy configurations.
Wilson estimates his clients save up to 60 percent on pruning labor costs by using machines.
Berg agrees, saying he thinks growers can save 40 percent to 60 percent on their labor expenses with significant reductions in labor hours.
A few challenges to overcome
Norton says there has been a gradual increase in interest in machine pruning over the years. But two factors have largely tempered enthusiasm.
Wineries have been wary of mechanical pruning for fear it may affect fruit quality. In most cases, Norton says, fruit quality is not a problem if the crop load is managed.
Although vines may overcrop initially, Hibbits and Wilson say they do even out with time and proper management.
Many growers also are reluctant because once they convert to machine pruning, they may find it difficult to go back if it doesn’t work.
As a result, Norton recommends that interested growers seek help from a farm adviser or vineyard consultant to explore the available options.
In addition, he says growers need to communicate with their wineries before jumping into any mechanized system.