Post-bloom thinning with 6-benzyladenine improves apple fruit quality

The effect of the post-bloom thinning agent 6-benzyladenine (BA) on fruit quality was examined on both ‘Delicious’ and ‘Golden Delicious’ apple cultivars over a two year period in Tasmania. A standard program of bloom thinners was used in all trials prior to application of BA. Seed numbers were reduced markedly in ‘Delicious’ but only slightly in ‘Golden Delicious’. Fruit increased in firmness and soluble solids concentration in both cultivars with BA treatment. Pygmy fruit were produced by some treatments in one of the ‘Delicious’ trials. BA counteracted the fruit flattening effect of ethephon in the first year ‘Delicious’ trial but not in the second; BA had no effect on fruit shape of ‘Golden Delicious’. Overall, BA had a positive effect on fruit quality in the two apple cultivars studied. This study demonstrates that both temperature and time of application play an important role in the effectiveness of BA as a post-bloom thinner.