Gibberellic Acid Sprays Increase Berry Size and Reduce Shot Berry of ‘Vanessa’ Grapevines

Abstract

‘Vanessa,’ a red seedless table grape, is often recommended for planting in cool climates because berries have excellent color, crisp texture, and flavor. However, in its natural condition ‘Vanessa’ clusters tend to be loose with small berries and frequent shot berries. The application of gibberellic acid (GA) to correct these deficiencies was evaluated for four growing seasons at concentrations of 25 and 50 ppm when berry diameters averaged 3, 5, 7 and 9 mm. GA increased yield, cluster weight, berry weight, fruits soluble solids and juice pH and decreased the number of shot berries per cluster and cluster compactness. Applications of GA at 50 ppm when berries averaged 5 mm in diameter were most effective for increasing berry weight and fruit soluble solids while reducing the occurrence of shot berry. Cane pruning weights recorded for vines over the 4-year period indicate no reduction in vine size as a result of GA applications made directly to clusters.