Evaluating the Impact of Ethephon on Bud Break and Delayed Pruning on Cluster Count in Winegrapes
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Grapes are an important crop in the United States with most of their value towards winegrapes. Frost and freeze events are a major weather-related problem, and late spring freeze/frost can cause considerable yield loss for growers, thus affecting the wine industry. Although there are numerous methods of frost protection, many are impractical or are not very effective. This project focused on the use of ethephon as a tool to prevent late spring frost damage by delaying bud break in grapes, and the impact of delayed pruning on vine fruitfulness (cluster count). Ethephon treatments consisted of applying ethephon as a spray on dormant canes at a rate of 145 mg L^-1 (low) and 291 mg L^-1 (high) at five different timings: November, December, January, February, and March. The greatest delay in bud break was observed in vines treated with ethephon in January. The high rate was more effective than the low rate and highly dependent on cultivar, except for low rate applications in November which showed adverse effects by advancing bud break during the spring. The results of this study suggest that the use of ethephon as a tool to delay bud break requires further research before it can be recommended. In the delayed pruning study, eight cultivars and numbered selections were subjected to final pruning at 50% bud break and final pruning at 3 weeks after 50% bud break. Across the six cultivars and numbered selections under study, a 19-80% decrease in cluster count was observed. However, vine vigor as determined by shoot length and iii shoot diameter was not significantly influenced by the delayed pruning treatments. These results suggest that pruning three weeks after bud break can be detrimental to grape yield and is not recommended as a means to avoid or mitigate late spring frost damage.
Labay, Yessica Esmeralda (2018). Evaluating the Impact of Ethephon on Bud Break and Delayed Pruning on Cluster Count in Winegrapes. Master's thesis, Texas A & M University. Available electronically from