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.
B.S. Wilkins, R.C. Ebel, W.A. Dozier, J. Pitts, and R. Boozer
Esmaeil Fallahi, Bahar Fallahi, James R. McFerson, Ross E. Byers, Robert C. Ebel, Robert T. Boozer, Jim Pitts, and Bryan S. Wilkins
Effects of Tergitol-TMN-6 surfactant on blossom thinning (fruit set), fruit quality, and yield were studied in different cultivars of peach (Prunus persica [L.] Batsch) during 2003 to 2005, and in one cultivar of nectarine Prunus persica [L.] in one orchard and one cultivar of plum (Prunus domestica [L.]) in two orchards in 2004. In addition to Tergitol-TMN-6, effects of Crocker's fish oil (CFO) alone in three peach cultivars or in combination with lime sulfur in a nectarine cultivar were studied on fruit set, quality, and yield. Tergitol-TMN-6 at 5 mL·L–1 or higher rates, applied at about 75% to 85% bloom, reduced fruit set without russeting peach fruit. Peach fruit size was often increased by Tergitol-TMN-6 treatment. Applications of Tergitol at 20 mL·L–1 or 30 mL·L–1 excessively thinned peaches. Tergitol-TMN-6 at all rates burned foliage, but the symptoms disappeared after a few weeks without any adverse effects on tree productivity. Tergitol-TMN-6 at 7.5 mL·L–1 or 10 mL·L–1, applied either once at about 80% to 85% bloom or twice at 35% bloom and again at 80% to 85% bloom, reduced fruit set without any fruit russeting in nectarine. Tergitol-TMN-6 at 7.5 mL·L–1 to 12.5 mL·L–1 reduced fruit set in `Empress' plum. CFO at 30 mL·L–1 was effective in blossom thinning of some peach cultivars. A combination of lime sulfur and CFO was not effective in blossom thinning of nectarine. Considering results from several orchards in different locations in the Pacific Northwest over 3 years, Tergitol-TMN-6 is an excellent blossom thinner for peach, nectarine, and plum at rates of 7.5 to 12.5 mL·L–1, sprayed at a spray volume of 1870.8 L·ha–1 when about 75% to 85% blooms are open.