INCREASING THE SIZE OF THOMPSON SEEDLESS GRAPES BY MEANS OF 4-CHLOROPHENOXYACETIC ACID, BERRY THINNING AND GIRDLING

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Abstract
The separate and combined effects of dip applications of 4-chlorophenoxyacetic acid, berry thinning, girdling, and girdling and berry thinning on Thompson Seedless grapes were studied in 1950 and 1951. Clusters treated with growth-regulator developed larger berries, and were usually heavier, than corresponding undipped clusters. In one expt. half of each of the Thompson Seedless vines was sprayed with 4-chlorophenoxyacetic acid at a concn. of 5, 15, or 25 ppm. At harvest the sprayed berries were usually about 30% heavier than the untreated controls. Pedicels on clusters sprayed with growth-regulator were more firmly attached, and there was less shatter of berries from the treated than from the untreated clusters.