Effects of Daminozide and Paclobutrazol Treatments on Fruit Ripening and Storage Behavior of ‘McIntosh’ Apple

Foliar daminozide (DZ) and paclobutrazol (PBZ) applications delayed apple ( Malus domestica Borkh.) fruit maturation and ripening at harvest the year of treatment. There was little effect on juice soluble solids or mean fruit weight. Following 24 weeks of air storage, treated fruit were firmer and displayed less core browning than those untreated. Trunk-drench or soil-spray applications of PBZ had little or no effect on any of these quality or physiological parameters of the fruit. In the year after treatment there were no residual effects of either DZ or PBZ on any fruit physiological parameters, despite significant PBZ-induced reductions in shoot growth, fruit size, seed number, pedicel length, and alterations in fruit shape. Chemical names used: butanedioic acid mono(2,2-dimethylhydrazide) (daminozide); β-[(4-chlorophenyl)methyl]-α-(1,1-dimethylethyl)-1 H -1,2,4-triazole-1-ethanol (paclobutrazol).