Early gibberellic acid sprays increase firmness and fruit size of 'Sweetheart' sweet cherry

Abstract

Growers in British Columbia, the U.S. Pacific Northwest and increasingly in other regions of the world apply gibberellic acid (GA) to increase fruit size, improve fruit firmness and delay maturity of sweet cherries (Prunus avium L.). The recommendation in BC has been to apply a single spray of 20 ppm GA at the straw-yellow stage of fruit development. The objective of this trial was to determine if the timing of the gibberellic acid spray has an effect on 'Sweetheart' sweet cherry fruit yield and quality. Treatments consisted of four timings of 20 ppm GA beginning in mid-June. There were two applications before the straw-yellow stage, the third spray coincided with the straw-yellow stage, and the fourth timing was about one week later. Fruit were harvested when non-treated control fruit were mature, and again one week later. Yield per tree, average fruit weight, rain-induced cracking, fruit firmness, total soluble solids, pH, and titratable acidity were determined for a sub-sample of fruit. Yield was not affected by the GA treatment. Fruit size was increased by about 1 g per fruit and fruit firmness increased by 15% when treated with GA. Fruit size and fruit firmness responded linearly to the GA applications with earlier sprays having the largest and firmest fruit.