Impact of Post-flowering Chemical Thinning on the Fruit Yield and Quality Metrics in ‘Fuji Suprema’ Apple Trees

Abstract

Under the climate variability conditions of southern Brazil, post-flowering thinning is a safer practice than thinning during flowering. This study aimed to evaluate the effect of the application of post-flowering thinning agent on ‘Fuji Suprema’ apple when used in combinations. The experiment was carried out in an experimental orchard located in the municipality of Caçador, Santa Catarina, Brazil during the 2017 to 2020 harvest seasons. We tested treatments combining Benzyladenine (BA) with Ethephon (ET) or Metamitron (MM), as well as individual applications of each product at different concentrations on apple fruits. Applications were made individually or in tank mixes during post-flowering periods, with manual thinning when fruits were 8 to 12 mm in diameter and chemical thinning at 15 to 20 mm in diameter.  Treatments were as follows: 1. Control (manual thinning); 2. BA (400 ml/100 L) + ET (200 ml/100 L); 3. BA (400 ml/100 L) + MM (100 g/100 L); 4. BA (600 ml/100 L); 5. ET (240 - 200 ml/100 L); MM (150 ml/100 L); MM (150 ml/100 L) + ET (200 ml/100 L). The results showed that the combination of Metamitron with Benzyladenine or Ethephon effectively regulated fruit set and enhanced fruit quality, making these combinations suitable for thinning under southern Brazil conditions.