Effect of early-season zinc sprays on ‘Golden Delicious’ apple

Abstract

A factorial field trial was carried out in a ‘Golden Delicious’ apple orchard in the Elgin area to test the hypothesis that early- season zinc (Zn) sprays exacerbate russet, and to determine the stage of development at which Zn sprays are most effective. The incidence of stem-end russet was not consistently affected, relative to the control, by single sprays of Zinc Max^reg (at solution concentrations up to 13.0g Zn 100 I⁻¹), Zinc Metalosate^reg (9.1g Zn 100 I⁻¹) or zinc oxide (20g Zn 100 I¹), applied up to 10 days after full bloom. Increased retiform russet was observed where zinc oxide was applied at 40g Zn 100 I⁻¹. Zinc sprays which were applied 10 days after full bloom were more effective in promoting increased leaf zinc levels and, possibly, increased shoot length, than sprays which were applied at green tip or at full bloom.