2025 Volume 24 Issue 4 Pages 307-316
High temperatures during the ‘Kyoho’ grape ripening period result in poor coloring. In recent years, high temperatures associated with global warming and expansion of seedless cultivation areas highlight the urgent need to prioritize this issue. This study was aimed to determine an effective method of applying a novel S-ABA pesticide on ‘Kyoho’ grapes. The results showed that hand-spraying a 100-fold solution (S-ABA at 1000 ppm) on clusters at the onset of coloring improved color development, reduced sugar and acid contents, and increased the sugar-acid ratio. Similar color development was observed for dilution ratios of 100 (S-ABA at 1000 ppm) and 200 (S-ABA at 500 ppm), with treatment applied from berry softening to two weeks after the onset of coloring. Neither treatment caused practical issues. Furthermore, fruit surface staining caused by spraying S-ABA-containing liquid can be reduced using equipment with a small average particle size, such as a fine nozzle or compressor spray gun. However, to obtain a consistent color-improvement effect, measures to prevent uneven spraying, such as increasing the amount of liquid sprayed, are necessary.
