The potential of a vegetable-based oil to delay bud burst while maintaining fruit sugar accumulation

Abstract

Yield loss and delayed fruit ripening due to spring, post-bud burst freeze injury is an economic challenge for many grape growers all over the world. A field trial was conducted in 2014 and 2015 to assess the efficacy of a vegetable-based oil (Amigo) to delay bud burst, hence reducing the chance of a damaging frost event, without negatively impacting grape production and fruit composition. Amigo was applied at 10% (v/v) once during the dormant season on Vitis vinifera cvs. Lemberger and Riesling. Application of Amigo significantly delayed bud burst and other key phenological stages (bloom and veraison) in both years. Vines treated with Amigo reached 50% bud burst six to 11 days later than control vines. At bloom, shoots of Amigo-treated vines were shorter than those of the control vines, but there were no differences in pruning weight between treatments. Overall, application of Amigo oil did not affect fruit chemistry at harvest. Amigo-treated vines, however, had lower crop yield (lower cluster weight) as compared to control vines suggesting potential oil phytotoxicity (e.g., bud injury, compromised flower development) effects. In a subsequent field study initiated in 2017 at the same site, Amigo applied at either 8 or 10% concentration did not cause primary bud necrosis in either Lemberger and Riesling vines. This suggests that Amigo did not reduce primary bud survival as compared to control vines.