Delay of Bud Break on ‘Edelweiss' Grapevines with Multiple Applications of Amigo Oil and NAA

‘Edelweiss’ is an important grape cultivar grown in the Midwestern part of the USA.  It is one of the earliest cultivars in the vineyard to break bud, making it very susceptible to late spring freezes.   ‘Edelweiss’ primary buds produce a significant amount of fruit, while unlike many other hybrids, the secondary and tertiary buds will have little to no yields, thus making it important to protect the primary buds from a late freeze.  The objective of this research was to determine if multiple applications of Amigo Oil or naphthaleneacetic acid (NAA) achieve a greater bud delay when compared to single applications.  ‘Edelweiss’ vines were treated in January, January and February or January, February and March.  Amigo Oil was applied at 10% (v/v) and NAA at 1000 mg/L with a custom built all-terrain vehicle (atv) sprayer.  All treatments of oil led to a significant bud break delay ranging from 3 to 11 days as compared to the control.  Buds treated with NAA showed no significant delays when compared to the oil or control treatments.  None of the treatments resulted in negative effects on harvest parameters such as yield or fruit characteristics.  A controlled laboratory experiment was also conducted, where single bud cuttings were forced in 200 mg/L 8-hydroxyquinoline citrate and 2% sucrose at 25° C under 12 hour days.  Treatments of one, two, and three applications of Amigo Oil and 1000 mg/L NAA were applied to single buds at weekly intervals.  Julian days until bud break were recorded and treatment-related bud break-delays were observed.  Two and three applications of oil significantly delayed bud break from 14 to 24 days.  All NAA treatments led to significant bud delay ranging from 6 to 9 days. Grape growers in climates with the potential of late spring freezes may consider the use of Amigo Oil as a potential means to protect their vines from frost injury.