Efficiency of California Trunk Shaking Pistachio Harvesters

Pistachios are long-lived with an extended juvenility; they generally require 8 to 10 years to achieve full bearing.  Pistachios have been harvested by trunk shakers since the industry was established in the 1970s.  Some orchards are now over 30 years old with trunk girths over 30” in circumference.  Preliminary data in 2009 indicated trunk shaking harvester efficiency was decreasing with increasing trunk girth.  In September 2010, 4 commercial and 2 experimental trunk shakers were tested on trees ranging from 30 to over 50 inches in girth.  The trees were shaken for 8 seconds, followed by hand gleaning.  Both samples were field weighed, hulled, dried and graded using standard industry grading procedures.  The resulting calculated trunk shaker final percentage efficiency and grading analysis demonstrated 79% to 86% final efficiency for the commercial shakers versus a significantly better 96% average final for the two experimental trunk shakers.  A regression analysis demonstrated 30% of the decrease in efficiency was associated with the increasing trunk girth.  These results strongly suggest the pistachio industry should begin evaluating improved trunk shaking technology, pruning that enhances trunk shaker efficiency, and alternative harvesting technologies versus the economics of replanting orchards.