Effects of prohexadione-Ca and GA4+7 on scarf skin and fruit maturity in apple

Abstract

A series of experiments were undertaken to compare the effects of individual and combined applications of GA4+7 and prohexadione-Ca (P-Ca) on scarf skin and fruit quality parameters on red strains of 'Rome Beauty' and 'Gala' apples. Three applications of GA4+7 at 10-day intervals beginning at petal fall (PF) significantly reduced scarf skin severity in all experiments. A single application of P-Ca at PF had no effect on scarf skin in one experiment but reduced scarf skin severity in two further experiments. Combining P-Ca with the first of three GA4+7 sprays as a tank mix reduced the severity of scarf skin more effectively than either material alone in two of three experiments at P < 0.05 and in all three experiments at P < 0.10. Combining P-Ca with the first application of GA 4+7 as a tank mix generally reduced scarf skin as effectively as applying P-Ca and the first GA4+7 spray two days apart, although in one experiment, greater scarf skin control was achieved when P-Ca was applied 2 days after the first GA4+7 spray. A single application of P-Ca at PF consistently reduced, and three applications of GA4+7 consistently increased, mean fruit weight at harvest compared with the control. The economic benefits as a result of reducing scarf skin severity with P-Ca and GA 4+7 sprays will need to be balanced against the negative effect of P-Ca on mean fruit weight. There is no antagonism between early season P-Ca and GA4+7 sprays for scarf skin control, and P-Ca may increase the efficacy of GA4+7 sprays for scarf skin control in apple.