The effects on budbreak of garlic paste, garlic oil, diallyl disulfide, and calcium and hydrogen cyanamides were examined in greenhouse-grown mature Pione (Vitis vinifera x V. labruscana) and potted Thompson Seedless (V. vinifera) grapevines not exposed to chilling. After the first crop from plants grown in greenhouses was harvested, all canes were pruned to five or seven buds so that the second crop was produced within one year. The upper cut surfaces of single-bud cuttings from the pruned Pione canes was promptly painted with a paste of fresh garlic, 20% garlic oil, 20% diallyl disulfide, the supernatant of a 20% suspension of CaCN2, or 1.4% or 2.8% H2CN2. All of the substances gave earlier budbreak than in the control treated with distilled water. The effects of CaCN2 and H2CN2 were greatest, followed by diallyl disulfide, garlic oil, and garlic paste, in order of decreasing effectiveness. CaCN2 and H2CN2 gave a more uniform timing of budbreak when painted on the upper half of the cutting (the cut surfaces were not treated) than when the upper cut surface only was treated. With Thompson Seedless cuttings, 20% diallyl disulfide painted on the upper cut surface accelerated budbreak and increased the rate of budbreak; garlic paste had similar but weaker effects. The painting of 2.5% H2CN2 on the upper cut surface of cuttings strongly inhibited budbreak, although the first date of budbreak was slightly earlier than in the control. When cut surfaces of Pione canes were treated, budbreak was earliest with 70% diallyl disulfide, followed by garlic paste; 100% garlic oil inhibited budbreak. Painting of the entire cane except for the cut surface of Thompson Seedless vines with 2.5% H2CN2 was the most effective for improving budbreak. Treatment with 20% diallyl disulfide resulted in a rate of budbreak that was not uniform, although the first budbreak was accelerated. In Pione vines, the mean number of flower clusters that developed on the shoots was unaffected by treatment, but in Thompson Seedless vines, there were fewer clusters after treatment with H2CN2 than after treatments with garlic paste or diallyl disulfide.
- Copyright 2000 by the American Society for Enology and Viticulture