Authors: TAE KWON SON, JUNG HEE KIM, CYREN RICO, SANG CHUL LEE, IL KYUNG CHUNG
Abstract: Effects of calcium nitrate (CN) and sodium sulfate (SS) blossom thinning agents applied after self-incompatibility control substance (SICS) treatment on the fruit set rate and quality of apple were investigated for 2 cropping seasons. CN and SS at 0.1% and 0.2% concentrations were applied once (3 or 4 days after SICS treatment) or twice (3 and 5 or 4 and 6 days after SICS treatment). Commercial Japanese flower thinning agent (FTA: Ekoruki) treated and untreated apple trees were used as treated and untreated controls. SICS was sprayed 7 days before full bloom. Both agents showed a fertilizing effect in 'Hongno', improving its fruit yield and quality. SS obtained 29.8% and 36.3% thinning rates in the central floret of 'Fuji'. Both CN and SS were effective in 'Gala', which induced a lower fruit set than SICS treated plants. Earlier and double applications of CN and SS at 0.2% concentration resulted in a higher thinning rate and improved fruit quality in 'Gala'. Results also showed similar thinning efficacies in Ekoruki, CN, and SS.
Keywords: Blossom thinning, fruit set, self-incompatibility
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