Effects of different pH sprays on the efficiency of prohexadione-Ca in sweet cherry trees

In 2003 and 2004, young ‘Kordia’ sweet cherry trees were sprayed with prohexadione-Ca (Pro-Ca) to control tree growth and stimulate flower bud setting. A rate of 200 mg Pro-Ca l^-1 × 2 dissolved in various pH-buffered (6.0-4.5) aqueous solutions was used. Regardless of the acidity of the spray solution applied, the trees treated with Pro-Ca were characterised by reduced shoot and internode length, greater number of shoots (2003) and increased total shoot extension (2004) relative to the control. In both years, Pro-Ca applied in a pH-4.5 buffer solution contributed to an increase of flower bud clusters on current-season shoots. However, there were no significant differences among Pro-Ca/pH treatments either in the vegetative or generative characteristics studied. Two years after Pro-Ca application, no residual effects were found in the studied tree characteristics.