Development and Control of Russet and Scarf Skin

Russet and scarf skin are the consequence of aberrant development of the epidermis and cuticle of apple fruit that can reduce crop value of some cultivars/strains.  Russet may result from a variety of stimuli including fungi, insects, freezing temperatures around the time of bloom, high humidity and precipitation in the weeks after bloom, or some crop protection sprays.  Scarf skin results from a separation of the fruit cuticle from underlying epidermal cells and is more obvious on heavily pigmented cultivars.  Multiple applications of a proprietary mixture of 15-20 mg×L^-1 GA₄₊₇ during the first three to four weeks after petal fall have been shown to reduce the severity of both russet and scarf skin.  Somewhat paradoxically, the gibberellin biosynthesis inhibitor prohexadione-calcium has also been shown to reduce the severity of both russet and scarf skin, either alone or additively when combined with GA₄₊₇.