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In order to determine effective spray of lime sulfur mixture for flower thinning in mature pear trees (Pyrus pyrifolia cv. Niitaka), it was sprayed to the blossom clusters up to four times at different phenological stages of the pear flowers either from terminal buds or from axillary buds. The multiple application exhibited flower thinning effect with various degrees. The triple application effectively thinned the flowers at a rate of more than 60% in terms of the rate of fruit set. However, the double application was not sufficient to thin the flowers. Furthermore, the quadruple application had no additional effect on flower thinning compared to the triple application. When lime sulfur mixture was sprayed to the blossom clusters based on the phenological stage of the flowers from terminal buds, the flowers from terminal buds were found to be more susceptible to lime sulfur mixture than those from axillary buds. When its multiple application except the triple application was done based on the phenological stage of the flowers from axillary buds, inversely, the flowers from axillary buds were more susceptible to lime sulfur mixture than those from terminal buds. The multiple application also reduced the proportion of fruiting cluster with the same tendency as in the reduction of the rate of fruit set and the fruit number within the fruiting cluster, leaving less than two fruits. In addition, the multiple application greatly reduced the time needed for the subsequent hand thinning of fruits up to the rate of 290 h/㏊. Thus, flower thinning in pear trees could effectively be done by using multiple sprays of lime sulfur mixture before the blooming and after the pollination of the third and the fourth flowers.
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