Evaluating Ethephon Use to Remove Tart Cherries from Non-Bearing Trees

Project goal: Determine the effectiveness of ethephon and two blossom caustic materials for fruit removal in young tart cherry trees.

Project description:  Growers have traditionally used gibberellic acid (GA) at high rates to remove fruit from non-bearing trees.  This strategy has been successful for the past 25 years, but in recent years, this PGR has not removed fruit adequately and had resulted in overset trees, which have a higher probability of runting out.  In 2018, a trial was designed to test different rates and timings of ethephon to remove fruit.  Ethephon was applied at five different timings (1st white, 50% bloom, 100% bloom, petal fall and shuck split) and four different rates (50ppm, 100ppm, 200ppm and 400ppm) to 5 year-old Montmorency tart cherry trees at the NWMHRC.  Treatments were applied with a hand-gun sprayer to four single tree replicates.  Blossoms were counted on 15 May 2018 on branches with greater than 150 flowers.  Branches were clearly marked and we returned to count the number of fruit on 19 June 2018.  Fruit quality was measured on 12 July 2018 for weight, brix and pull force.   In 2019, the ethephon treatments were refined based on 2018 data and included blossom caustic materials.  Ethephon was applied at four rates: 100ppm, 200ppm, 400ppm, and 800ppm and at two timings: first white – full bloom (23 May) and full bloom – petal fall (29 May).  Ammonium thiosulfate (ATS) and lime sulfur oil (LSO) were applied at late bloom (23 May) and early petal fall (29 May) at 2%, 4%, and 8%.  Fruit set was collected in the same manor as in 2018 but we also included a damage rating because the caustic materials caused significant leaf burn.  In 2020, we analyzed return fruit set in the ATS and LSO treated trees.

Project lead/collaborators: Nikki Rothwell and Todd Einhorn

Funding sources: Michigan Cherry Committee

Start year: 2018

End year: 2020

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