Response of Grapevines to Soybean Oil Application

Abstract

Chancellor, Chambourcin, and Chardonel grapevines were treated with soybean oil-based adjuvants and then compared to untreated (control) vines for phytotoxicity, date of budbreak, yield components, and fruit composition. The purpose of dormant oil application was to delay budbreak without affecting date of fruit ripening, yield, or fruit composition. In the first year, Prime Oil and Amigo were applied at a 10% concentration (v/v) to runoff with a backpack sprayer on three different dates during the dormant season. Prime Oil but not Amigo was phytotoxic to dormant buds in all three cultivars. Both oil treatments led to a significant budbreak delay in all cultivars ranging from 1 to 20 days as compared to control vines. A reduced carbon dioxide exchange from oil-treated buds was associated with a delay in bud development. At harvest, cultivars that sustained bud injury from Prime Oil treatment had reduced yields and delayed fruit maturity; conversely, Amigo did not affect yield components or fruit composition. In the second year, six rates (0%, 2%, 4%, 6%, 8%, and 10%) of Amigo oil were applied to Chambourcin and Chardonel grapevines and none was phytotoxic to either cultivar. Rates of 8% and 10% (v/v) delayed budbreak in Chardonel, but not in Chambourcin. None of the rates resulted in any deleterious effects on fruit set, yield components, or fruit composition in either cultivar. Grapegrowers may consider soybean oil application as an efficient and affordable practice that may protect early cultivars against spring frost injury by delaying the date of budbreak.