A study initiated in Spring 1995 examined the influence of gibberellic acid (GA3) application timing on the return fruitfulness of Thompson Seedless and Flame Seedless table grapes. Vines treated with GA3 at prebloom, bloom, or berry set were compared to vines treated at prebloom + bloom + berry set and nontreated vines. Application amounts for each cultivar and timing were based on commercial label recommendations. Nodes from each treatment were collected in mid-winter and dissected, and their viability and fruitfulness were recorded. Bud viability (shoots per bud) and fruitfulness (clusters per shoot) also were evaluated at budbreak in 1996. The results indicate that GA3 applications at prebloom and bloom are most detrimental to bud viability and cluster initiation in these cultivars.
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