This study was conducted to determine efficacy of Tergitol TMN-6 in thinning peach blossoms. A pretest was conducted and demonstrated no difference between TMN-6 and TMN-10 in efficacy when applied at full bloom or petal fall and at rates of 20 and 40 mL·L-1. In the main test, Tergitol TMN-6 was sprayed once at 10, 20, or 30 mL·L-1 at full bloom or petal fall and compared to an unsprayed control for 3 years. Tergitol caused widespread necrosis of flower parts including sepals, petals, pistils, stamens and peduncles. There was a difference among chemical treatments with more fruit removed at higher concentrations, although the amount of fruit removed was similar for the 20 and 30 mL·L-1 rates. There was no difference in thinning response at full bloom or petal fall, indicating a wide window of efficacy. There was also a difference among years, which was apparently not related to temperature or relative humidity during time of application. Tergitol caused some leaf yellowing and tip burn especially at the higher rates when leaves were present, but the trees did not appear to be seriously affected. Fruit weight was either not affected or larger in some years from treatment. Unlike higher concentrations, tergitol at 10 mL·L-1 did not negatively impact fruit number per tree at harvest. At harvest, fruit weight, skin blush, firmness, and soluble solids at harvest were not affected by treatment. Tergitol TMN-6 proved to be an effective thinning agent and when applied from full bloom to petal fall at 10 mL·L-1 it did not adversely affect the tree or fruit.
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