Effect of hydrogen cyanamide and promalin on flowering, fruit set and harvest time of ‘Flordaprince’ peach (Prunus persica (L.) Batsch) in subtropical Australia

Abstract

Hydrogen cyanamide (H2NCN) and promalin (6-benzylaminopurine + gibberellic acids 4+7) were applied either alone or in combination to ‘Flordaprince’ peach trees at concentrations of 0.5% and either 200 or 400 ppm respectively. When applied in late autumn (9 May) both compounds stimulated vegetative budbreak but promalin was ineffective in stimulating floral budbreak, induced a heavy drop of floral buds and reduced yields. By contrast, H2NCN stimulated floral budbreak and did not significantly increase floral bud abscission. Advanced flowering in H2NCN treated trees was translated into an earlier harvest with yields equivalent to control trees. When applied in early winter however (6 June) H2NCN was ineffective in promoting floral budbreak, induced significant floral bud abscission and reduced yields. Examination of these results in relation to previous studies in subtropical Australia indicates that simple calender schedulings for H,NCN spray application will not prove satisfactory. Efficient and safe use of this chemical for low-chill stonefruit will require development of an empirical measurement of bud phenological status.