“Edward Scissorhands” Replacing Hand Pruning

Two projects are underway in the Midwest to test and expand the use of mechanical grape vine pruning.  One project in Wisconsin will evaluate mechanical rough pruning for cold climate hybrids.   Another research project at Purdue University is looking at cutting edge technology to perform finer pruning using robotics.

During 2012, David Danzinger of Danzinger Vineyards in Alma, Wisconsin secured a grant from the USDA to study mechanical grape pruning in Wisconsin.  The $21,968 grant from the USDA Grants and Education to Advance Innovations in Sustainable Agriculture program will compare mechanical pruning to hand pruning for smaller hybrid vineyards.

David Danzinger discussing wine with customers at his winery in Alma, Wisconsin.

Meanwhile, researchers at Purdue University received $6 million to study how vineyard and apple orchard pruning can be further automated.  The USDA contributed $3 million which was matched by private and institutional funds according to a statement by Purdue.   University researchers are seeking to improve an automated pruner developed by Vision Robotics of San Diego.  Pulled by a tractor, the prototype pruner travels over grapevines using robotic arms guided by computers and laser sighting to trim mature vines.

Dr. Peter Hirst, Associate Professor of Agriculture at Purdue University, said the prototype pruner is intended to do they type of fine pruning that can currently only be done by humans with hand shears.  “What we’re developing is an “Edward Scissorhands” type of machine that can prune a vine down to a two bud spur with no human involvement,” he said.  The machine will be able to distinguish between vines, cordons and trellis wires, Hirst said.

Hirst said Purdue is in the first year of a four-year project to develop the pruner.  There is currently no timetable to demonstrate the robotic pruner.

Danzinger’s project does not have the science fiction appeal of the Purdue Project, but it’s much father along.  According to David Danzinger,  a Munckhof Barrel Pruner has been ordered.  The unit will work only on Vertical Shoot Position (VSP) trellised grapes.

“We purchased this brand because it has a simply design and is the only unit we could find that is made in North America with parts that are available at any local machine repair shop. Our unit is made in British Columbia,”  Danzinger said.

Danzinger’s will use his grant to study how mechanical pruning affects northern hybrid grape vines. This will include over wintering, quality and quantity of grapes, size of clusters, and disease and insect pressure.  No money from the grant may be used to purchase equipment.

“We will be studying Frontenac, Frontenac Gris, Marquette and LaCrescent at three regional vineyards. We will also observe if mechanical pruning has any effects on the other cold varieties we have at our vineyard  which include Prairie Star, Brianna, St Pepin, St Croix and Lacrosse,” he said.

One of the vineyards that will be testing the mechanical pruning equipment on cold climate grapes is Whispering Pines Vineyard in Viroqua, Wisconsin. According to Ron Haakenson at Whispering Pines, “They want us to try the pruner on a low cordon varietal, probably our LaCrosse.  We will not be changing anything about how the grapes are trellised.”

See related story: Grape Production Expands in Vernon County Wisconsin

Most vineyards in Washington state over 75 acres have barrel pruners according to Grant De Vries of Vine Tech Equipment in Prosser, Washington.  De Vries said that spur pruning is more common than cane pruning in Washington and therefore lends itself to mechanical barrel pruning.

John Thull, the vineyard manager at the University of Minnesota, said he thinks that mechanical pruning is better suited for hybrid grapes that are spur pruned and grown on a VSP trellis.  He concurs with De Vries in Washington about the limitations of using mechanical pruning on cane pruned vines.

“With cane pruning, you’d have to first pull down the canes you want to keep for fruiting before using the machine, otherwise every cane is automatically cut short leaving only spurs to work with. With mechanical pruning, I would still want to go back and do some fine pruning by hand to clean up the vines and ensure quality,” Thull said.

For Danzinger’s pruning research, there will be a field day next spring to demonstrate the equipment.  (Demonstration is now scheduled for March 16th, 2013, please see MWP “Professional Calendar” for more info.) There will also be a field day in the summer to demonstrate trimming of extra mid-season growth with a mechanical trimmer.   The dates for the demonstrations will be published on the Wisconsin Grape Growers Association Website at http://wigrapes.org/

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