Dwayne B. Visser

Gibberellins Stimulate Lateral Branch Development in Young Sweet Cherry Trees in the Orchard

Previous studies showed that successful stimulation of lateral branch development from 1-year-old wood in young sweet cherry trees without reliance on pruning could be accomplished if suitable cytokinin- or cytokinin/gibberellic acid-containing products were applied to assure penetration into active tissues. The goal of the trials reported here was to determine the potential for stimulating lateral branching by applying gibberellic acid alone under similar conditions. Three commercially available products containing gibberellic acid were evaluated. Treatments included the isomers GA3, GA4, and GA4 combined with GA7. All gibberellic acid isomer/formulations were similar in their ability to stimulate branching from lateral buds on 1-year-old wood. In one trial, GA4+7 alone was nearly as effective as the cytokinin 6-benzyladenine. Combining the surfactant Pentra-bark with gibberellic acid resulted in successful branch induction without the need to apply gibberellic acid to scoring or nicking cuts in the bark.

Stimulation of Lateral Branch Development in Young Sweet Cherry Trees in the Orchard Without Bark Injury

The goal of the trials reported here was to determine the potential for replacing physical disruption of the bark layer with appropriate surface-active chemical products added to bioregulator solutions applied to unpruned 1-year-old sweet cherry (Prunus avium L.) shoots to induce lateral branching. Two surfactant products, Pentra-bark (Quest Products Corp., Louisberg, KS.) and Syl-Tac (Wilbur-Ellis Co., Fresno, CA), combined with Promalin (PR, Valent BioSciences, Walnut Creek, CA) and applied to uninjured bark resulted in approximately the same increase in branching as produced by PR applications to scoring or nicking cuts. Surfactant concentrations higher than 1% v/v were usually necessary to produce increased branching. High concentrations of PR were not effective unless supplemented with a surfactant. Painting active solutions in 3–4 cm wide bands every 30 cm was just as effective as painting those solutions along the length of the outward-facing side of 1-year-old shoots. Use of appropriate surfactants to penetrate the bark barrier can eliminate hand labor for cutting the bark, reduce risk of worker injury, and reduce the risk for bacterial canker infection of trees during branch induction on 1-year-old shoots of sweet cherry