Cluster removal during the growing season is a widely utilized vineyard management practice aiming to balance crop load to the capacity of the vine to ripen the fruit. Research was undertaken over two growing seasons (2008-2009) in Hawke’s Bay, a cool climate region of New Zealand, to establish the influence of different times of crop removal on Merlot vine growth and fruit and wine composition. The test vineyard was high-yielding, to 23 t/ha, and vigorous. A commercial standard of apical cluster thinning to remove 20 clusters per vine from vines with ca 44 clusters in 2008 and ca 47 in 2009, was carried out on uniform vigour, 7yo grafted Merlot vines at nine times between prebloom and six weeks post veraison. The 2009 season was naturally higher yielding. Timing of crop removal had no significant effect on vine vegetative growth in terms of enhanced shoot growth as measured by cane weights at pruning, or canopy leaf density. Time of thinning also had no effect on overall grape yield, cluster weight, and berry weight. There were limited effects on fruit ripeness in one season (2009) at the veraison time of thinning only, with increased Brix and lower TA levels. Berry anthocyanin concentrations were enhanced by cluster thinning in 2008, and more so when undertaken at or soon after veraison. There was however no influence of removal timing on anthocyanin levels and total phenolics in the wines. Grape ripeness, must and wine composition tended to respond more from crop removal at veraison than the other times evaluated. Data suggest that vine response was modified by excessive leafiness and shading.
Petrie, P.R. and Clingeleffer, P.R. (2006) Mechanical and/or Hand Thinning of Cabernet Sauvignon. Australian Journal of Grape and Wine Research, 12, 21-29. http://dx.doi.org/10.1111/j.1755-0238.2006.tb00040.x
Wolf, T.K., Dry, P.R., Iland, P.G., Botting, D., Dick, J., Kennedy, U. and Ristic, R. (2003) Response of Shiraz Grapevines to Five Different Training Systems in the Borossa Valley, Australia. Australian Journal of Grape and Wine Research, 9, 82-95. http://dx.doi.org/10.1111/j.1755-0238.2003.tb00257.x
Chapman, D.M., Matthews, M.A. and Guinard, J.-X. (2004) Sensory Attributes of Cabernet Sauvignon Wines Made From Vines with Different Crop Yields. American Journal of Enology and Viticulture, 55, 325-334.
Reynolds, A.G., Yerle, S., Watson, B., Price, S.F. and Wardle, D.A. (1996) Fruit Environment and Crop Level Effects on Pinot Noir. III. Composition and Descriptive Aanalysis of Oregon and British Columbia Wines. American Journal of Enology and Viticulture, 47, 329-339.
Reynolds, A.G., Schlosser, J., Power, R., Roberts, R., Willwerth, J. and de Savigny, C. (2007) Magnitude and Interaction of Viticultural and Enological Effects. l. Impact of Canopy Management and Yeast Strain on Sensory and Chemical Composition of Chardonnay Musque. American Journal of Enology and Viticulture, 58, 12-24.
Coombe, B.G. (1995) Adoption of a System for Identifying Grapevine Growth Stages. Australian Journal of Grape and Wine Research, 1, 100-110. http://dx.doi.org/10.1111/j.1755-0238.1995.tb00086.x
Ough, C.S. and Ngaoka, R. (1984) Effect of Cluster Thinning and Vineyard Yields on Grape and Wine Composition and Wine Quality of Cabernet Sauvignon. American Journal of Enology and Viticulture, 35, 30-34.
Bravdo, B., Hepner, Y., Loinger, C., Cohen, S. and Tabacman, H. (1985) Effect of Crop Level and Crop Load on Growth, Yield, Must and Wine Composition, and Quality of Cabernet Sauvignon. American Journal of Enology and Viticulture, 36, 125-131.
Prajitna, A., Dami, I.E., Steiner, T.E., Ferree, D.C., Scheerens, J.C. and Schwartz, S.J. (2007) Influence of Cluster Thinning on Phenolic Composition, and Antioxidant Capacity in Chambourcin Wine. American Journal of Enology and Viticulture, 58, 346-350.
Guidioni, S.A., Ferrandino, A. and Novello, V. (2008) Effects of Seasonal and Agronomical Practices on Skin Anthocyanin Profile of Nebbiolo Grapes. American Journal of Enology and Viticulture, 59, 22-29.
Mattii, G.B. and Ferrini, F. (2005) The Effects of Crop Load on “Sangiovese” Grapevines. In: Williams, L.E., Ed., ISHS Acta Horticulturae 689: VII International Symposium on Grapevine Physiology and Biotechnology, ISHS, Davis, California, USA, 239-242
Nuzzo, V. and Matthews, M.A. (2006) Response of Fruit Growth and Fruit Ripening to Crop Level in Dry-Farmed Cabernet Sauvignon on Four Rootstocks. American Journal of Enology and Viticulture, 57, 314-324.
Pena-Neira, A., Caceres, A. and Pastenes, C. (2007) Low Molecular Weight Phenolic and Anthocyanin Composition of Grape Skins from cv. Syrah (Vitis vinifera L.) in the Maipo Valley (Chile): Effect of Clusters Thinning and Vineyard Yield. Food Science and Technology Internationals, 13, 153-158. http://dx.doi.org/10.1177/1082013207077920
Jackson, D.I. and Lombard, P.B. (1993) Environmental and Management Practices Affecting Grape Composition and Wine Quality—A Review. American Journal of Enology and Viticulture, 44, 409-430.
McDonald, C., Bell, S.-J., Lantzke, N. and Kennison, K. (2005) Bunch Thinning: When Is the Best Time to Thin, and Is It Worthwhile. Australian & New Zealand Grapegrower & Winemaker, Annual Technical Issue, 40-46.
Dokoozlian, N.K. and Hirschfelt, D.J. (1995) The Influence of Cluster Thinning at Various Stages of Fruit Development on Flame Seedless Table Grapes. American Journal of Enology and Viticulture, 46, 429-436.
Ferree, D.C., Cahoon, G.A., Scurlock, D.M. and Brown, M.V. (2003) Effect of Time of Cluster Thinning of Grapevines. Small Fruits Review, 2, 3-14. http://dx.doi.org/10.1300/J301v02n01_02
Keller, M., Mills, L.J., Wample, R.L. and Spayd, S.E. (2005) Cluster Thinning Effects on Three Deficit-Irrigated Vitis vinifera Cultivars. American Journal of Enology and Viticulture, 56, 91-103.
King, P.D., McClellan, D.J. and Smart, R.E. (2012) Effect of Severity of Leaf and Crop Removal on Grape and Wine Composition of Merlot Grapevines in Hawke’s Bay, New Zealand. American Journal of Enology and Viticulture, 63, 500-507. http://dx.doi.org/10.5344/ajev.2012.12020
Griffiths, E. (2001) Soils of the Heretaunga Plains—A Guide to Their Management. Grifftech and Hawke’s Bay Regional Council, Napier, 102 p.
Smart, R.E. and Robinson, M. (1991) Sunlight into Wine: A Handbook for Winegrape Canopy Management. Winetitles, Adelaide.
Iland, P.G., Cynkar, W., Francis, I.L., Williams, P.J. and Coombe, B.G. (1996) Optimisation of Methods for the Determination of Total and Red-Free Glycosyl Glucose in Black Grape Berries of Vitis vinifera. Australian Journal of Grape and Wine Research, 2, 171-178. http://dx.doi.org/10.1111/j.1755-0238.1996.tb00105.x
Iland, P., Ewart, A., Sitters, J., Markides, A. and Bruer, N. (2000) Techniques for Chemical Analysis and Quality Monitoring during Winemaking. Patrick Iland Wine Promotions, Campbelltown, 98-100.
Green, S. (2008) Measurement and Modelling the Transpiration of Fruit Trees and Grapevines for Irrigation Scheduling. In: Goodwin, I. and O’Connell, M.G., Eds., Acta Horticulturae 792: Proceedings of the Fifth International Symposium on Horticultural Crops, ISHS, Leuven, 321-327.
Kliewer, W.M. and Dokoozlian, N.K. (2005) Leaf Area/Crop Weight Ratios of Grapevines: Influence on Fruit Composition and Wine Quality. American Journal of Enology and Viticulture, 56, 170-181.