Fruit Set in Seedless Grapes Treated with Growth Regulators Alar, CCC and Gibberellin1

Abstract Growth retardants succinic acid 2,2-dimethyl hydrazide (Alar), (2-chloroethyl) trimethylammonium chloride (CCC), and potassium gibberellate (KGA 3 ) were tested as fruit-setting agents in 1967 and 1968 for poorly setting varieties of seedless grapes. Cluster and berry thinning was practiced on the control and treated vines. Pre-bloom Alar sprays at most concentrations from 250 to 2000 ppm failed to increase the number of berries per cluster or cluster weight, and showed a tendency to reduce average berry weight and total soluble solids. Pre-bloom CCC treatments from 500 to 1500 ppm gave increases in the number of berries per cluster and cluster weight, while average berry weight and total soluble solids were unaffected. Length of the newly formed internodes was reduced by CCC treatments of 500 and 1500 ppm while Alar at these concentrations had little effect.