Effects of succinic acid-2,2-dimethyl hydrazide (Alar) or scoring on growth and flower initiation of young apple trees

Abstract

Foliar sprays of the growth retardant succinic acid-2,2-dimethyl hydrazide (Alar) applied early in the spring on young non-bearing Delicious, Granny Smith, and Gravenstein apple trees reduced the extension growth and increased the amount of bloom in the following spring. Scoring (a knife cut completely around the trunk) in late October and during November on Granny Smith, and Gravenstein trees increased the amount of bloom in the following year. When scoring has performed in early December the response to flowering on Gravenstein variety was greatly reduced. Scoring reduced the extension growth on Granny Smith but not on Gravenstein variety. The use of either Alar or scoring offer practical ways of promoting earlier flowering and cropping of young non-bearing apple trees.