Growth regulation of pome and stone fruit trees by use of prohexanedione-Ca

Prohexadione-Ca is an inhibitor of late stages of gibberellin biosynthesis. This compound is under actual development for use as a growth retardant in different crops. Trials with prohexadione-Ca to control vegetative growth of apple, pear and (prune) plum trees were carried out over three seasons (1995-1997) in Poland. The following cultivars were used apple: 'Lobo', 'Gloster' and 'Jonagold', pear: Conference, plum: 'Stanley', 'Dabrowice' and 'Lowicz'. The growth retardant was used at concentrations ranging from 75 to 250 mg/L of active ingredient in one or two foliar treatments. It was shown that prohexadione-Ca is suited for regulating the growth of the investigated pome and stone fruits. It caused a significant reduction of vegetative growth, however, particular species and cultivars differed with their sensitivity to the compound and needed different concentrations. In several instances increases in yield and quality could be observed.