Control of apple russeting in a warm and dry climate

Russeting is one of the more important horticultural problems in apple (Malus X domestica) production worldwide. 'Smoothee' (cv. Golden Delicious), the major commercial strain grown in Israel, is susceptible to russeting. Israel's apple growing season is characterised by having a warm, dry climate, particularly during fruit set and the putative cell division stages of development. Treatment with gibberellins A4 and A7 (GA(4+7)) plus 6-benzyladenine (6-BA) to control russet formation has long been questioned, due to poor results in Israel. The efficacy of this hormonal treatment was re-evaluated following the induction of skin russeting by fogging trees and exposing fruit to high humidity. Fruit were most susceptible to fog-induced russeting up to 50 d after petal fall. GA(4+7) plus 6-BA treatment did not reduce fruit russeting dramatically. Multiple applications, beginning at petal fall, were effective only on fruit with slight russeting. Crop marketability was not significantly improved. Growers in a warm and dry climate, similar to Israel, should give serious consideration to the costly application of GA(4+7) as a routine procedure to reduce or control russet on apples.