Delaying Bud Break in ‘Edelweiss’ Grapevines to Avoid Spring Frost Injury by NAA and Vegetable Oil Applications

Delaying bud break is an approach to avoid spring frost damage. Field experiments were conducted during the winters of 2009 and 2010 at James Arthur Vineyards in Raymond, Nebraska to study the effect of spraying NAA and Amigo Oil on delaying bud break in ‘Edelweiss’ grapevines to avoid such damage. In 2009, the experiment consisted of five treatments: NAA (500, 750, and 1000 mg/l), oil applied at 10%, and the non-sprayed control. There were four application dates: January 6, February 3, March 3, and April 1. Bud break was evaluated throughout spring. During harvest, the number of clusters and weights were recorded. Berry samples were analyzed for pH, °Brix, and titratable acidity (TA). Pruning weights and number of clusters of the 2009 treated vines were recorded in March and August 2010, respectively. In 2010, NAA concentrations were 500, 1000, and 1500 mg/l, 10% oil, and the control. Application dates were: January 28, February 25, and March 25. Similarly to 2009, bud break was evaluated throughout spring, number of clusters and weights per vine were recorded, and berry samples were analyzed for the same parameters mentioned as in 2009. A forcing solution experiment was conducted on ‘Edelweiss’ canes collected on the same dates as the field experiments. For each date, 20 canes were headed back to the first five buds, then cut into five single-bud cuttings and the bases immersed in forcing solution. The same treatments as used in the field experiments were applied by adding one drop on each bud. Days to bud break and shoot length one week after bud break were recorded. In the 2009 field experiment, oil and NAA at 1000 mg/l significantly delayed bud break 2-6 days compared to the control. In 2010, oil applications significantly delayed bud break 8-12 days compared to the control and no significant differences were found between NAA at 1500 and 1000 mg/l. In both years, treatments had no significant effects on yields, cluster weights, berry weights, °Brix, pH, and TA. The forcing solution experiment showed a month, position, and treatment interaction regarding bud break delay in both years. No treatment effects were found regarding shoot length