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Growers should be careful using bud dissection results to estimate yield. Studies have found that bud dissections may explain from as low as 50% to as high as 90% or the variation in actual yield.4 Several years of data comparing bud dissections to actual yield will help growers interpret results with more confidence.10
Bud dissection sometimes strongly underestimates bud fruitfulness.11 This suggests that tiny inflorescences overlooked by inspectors may still produce clusters. Also, a random sample of all canes on a vines may show lower fruitfulness than a sample of the stronger canes favored by pruners. Growers must be careful to take a sample representative of the canes they expect will remain on the vine after pruning.
If bud analysis is accurate, a grower can calculate the average number of flower clusters per vine for different numbers of spurs or canes. Of course, there are limits to the number available. When pruners leave more spurs or canes, they may include more of the weaker or sub-standard choices.
Bud analysis can tell which nodes have the most fruit. If the buds on a 2-4 bud spur are unfruitful, longer spurs may be needed to include more fruit, or the grower may need to add a “kicker cane” or two.
However, because of apical dominance caused by auxins moving out along the spur, leaving more nodes on the cane tends to suppress sprouting of the nodes near the base.11 For example, if the first two buds have more fruit than the next two, retaining the fourth bud in pruning may actually reduce the number of bunches by suppressing bursting of the first bud. The grower needs accurate knowledge of which buds will bring the best return.
Growers are also leery of adding extra nodes on spurs (three or four bud spurs), because that makes the vines taller and harder to prune the following year.11
Virtually all of the material on inflorescence was taken from research and literature reviews given to me by Dr. Luis A. Sanchez, who studied bud differentiation for his Ph.D. dissertation at U.C. Davis and now works for E&J Gallo Winery. The Srinivasan paper is also a good review, but Dr. Sanchez includes that information in his review. Dr. Sanchez kindly reviewed the present paper.
1. Sánchez, Luis A., and Nick K. Dokoozlian. 2005. “Bud microclimate and fruitfulness in Vitis vinifera L” Am. J. Enol. & Vitic. 56:4 (2005).
2. Sánchez, Luis A., Nick K. Dokoozlian, and Martin C. Goffinet. 2007. “Variations in the nodes of Vitis vinifera L.: double compound buds” Proceedings of the 1st Annual National Viticulture Conference. July 18–20, 2997. Davis CA. See website or online pdf
3. Srinivasan, C., and M.G. Mullins. 1980. “Physiology of flowering in the grapevine—Areview” Am. J. Enol. & Vitic. 32 (1) 47–63.
4. Williams, L.E. 2000. “Bud development and fruitfulness of grapevines,” In Raisin Production Manual. L.P. Christiansen (Ed.) Pp. 24–29. University of California Division of Agriculture and Natural Resources, Oakland.
5. Vasudevan, Lakshmi, 1997. Anatomical developments and the role of carbohydrate or mineral nutrient deficiency in bud necrosis of Riesling grapevines. Ph.D. dissertation, Virginia Polytechnic Institute. See website
6. Collins, C., and B. Rawnsley. 2005. “Factors influencing primary bud necrosis (PBN) in Australian vineyards” Acta Hort. (ISHS) 689:81–86 VII International Symposium on Grapevine Physiology and Biotechnology. See website.
7. Bernard, Martina, Melissa Carew, Pamela Hurst, Paul Home, and Ary Hoffinann. 2003. “Integrated management of grapevine bud mites (Colomerus vitis) in Australian vineyards. Preliminary recommendations” In Strategic Use of Sulphur in Integrated Pest and Disease Management (IPM) Programs for Grapevines. FINAL REPORT to GWRDC. December 2003. See online pdf
8. Grape Pest Management, second edition. University of California, Division of Agriculture and Natural Resources. 1992.
10. Vasquez, Stephen, and Matthew Fidelibus. “Using grapevine bud dissection to assess yields” Univ. Of California, Coop. Ext., Fresno Co. Vine Lines, December 2006 issue.
11. Peacock, Bill, Anthony Tartaglia, and Matt Mills. 2006. “Red Globe pruning, bud fruitfulness, and crop load study” Univ. Of California, Coop. Ext., Tulare Co. Grape Notes, Vol. 3, Issue 7.