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May 2016 WINES&VINES 83 WINE EAST GRAPEGROWING alternative to traditional cluster thinning for reducing crop level and improving grape and wine composition (Gatti et al. 2012, Tardaguila et al. 2012). Crop- regulation achieved with cluster thinning and pre-bloom leaf re- moval is based on two different mechanisms: The first reduces the number of clusters, the sec- ond cluster weight. The increased interest in pre- bloom leaf removal over cluster thinning is related to its suitabil- ity for mechanization (Intrieri et al. 2008) and other desirable features such as improvement of canopy microclimate and de- crease of cluster compactness. However, relying on pre-bloom leaf removal to consistently re- duce yield to the desired level could be risky. In this sense, clus- ter thinning is a more conserva- tive approach because, unlike pre-bloom leaf removal, its se- verity can be decided upon esti- m a t i o n o f f i n a l y i e l d . EFFECT OF LEAF REMOVAL, TIMING AND GIBBERELLIN ON CLUSTER DEVELOPMENT Treatments 2007 2008 2009 2010 2011 2012 a Fungicides b Amendment and timing c Berries per centimeter (compactness) P, V LR (hand)………….TB 8.04 a 9.48 a 8.41 7.74 a 9.06 a 11.02 P, V LR (hand)………….PS 10.17 bc 11.31 b 9.19 9.28 b 12.78 b 12.44 P, V d LR (hand)………….V 10.72 c 11.84 b 10.34 P, V d 5 mg/L GA………….B 9.50 b 11.73 b 9.32 P, V e 10,25 mg/L GA……..B 9.38 b 10.03 a 7.86 7.74 a 9.80 a 11.79 P, V * 10.93 c 11.84 b 9.61 8.64 ab 12.97 b 12.28 P = 0.001 P = 0.002 P = 0.054 P = 0.009 P = 0.001 P = 0.175 Fungicides Amendment and timing c Berries per cluster P, V LR (hand)………….TB 65.2 a 67.4 58.6 45.3 a 65.9 a 83.9 P, V LR (hand)………….PS 83.2 bc 74.7 68.6 61.5 b 103.0 bc 97.4 P, V d LR (hand)………….V 83.2 bc 83.2 75.2 P, V d 5 mg/L GA………….B 78.8 abc 77.6 71.5 P, V e 10,25 mg/L GA……..B 75.5 ab 72.2 63.1 52.7 b 82.6 ab 92.7 P, V * 92.1 c 81.4 80.2 62.0 b 111.9 c 87.2 P = 0.020 P = 0.126 P = 0.174 P = 0.039 P = 0.001 P = 0.368 Fungicides Amendment and timing c Cluster weight (grams) P, V LR (hand)………….TB 112.0 a 105.5 90.0 a 71.9 a 95.4 a 124.0 P, V LR (hand)………….PS 142.8 cd 128.8 103.3 abc 93.8 b 147.9 b 134.3 P, V d LR (hand)………….V 139.3 bcd 123.0 107.5 bc P, V d 5 mg/L GA………….B 132.3 bc 119.0 113.8 c P, V e 10,25 mg/L GA……..B 124.8 ab 116.3 104.0 abc 74.4a 119.4 ab 136.5 P, V * 144.3 cd 124.3 104.5 bc 94.4 b 144.7 b 135.0 P = 0.001 P = 0.054 P = 0.023 P = 0.003 P = 0.004 P = 0.158 Fungicides Amendment and timing c Berry weight (grams) P, V LR (hand)………….TB 1.62 b 1.55 1.44 1.54 b 1.40 b 1.43 P, V LR (hand)………….PS 1.51 a 1.49 1.38 1.48 ab 1.38 b 1.39 P, V d LR (hand)………….V 1.50 a 1.49 1.44 P, V d 5 mg/L GA………….B 1.55 ab 1.47 1.49 P, V e 10,25 mg/L GA……..B 1.61 b 1.48 1.43 1.36 a 1.39 b 1.42 P, V * 1.49 a 1.43 1.39 1.47 ab 1.24 a 1.42 P = 0.013 P = 0.281 P = 0.223 P = 0.008 P = 0.002 P = 0.796 Chardonnay grape clusters studied at the Lake Erie Regional Grape Research and Extension Center. LR=leaf removal; GA=gibberellin a Fungicides: Botrytis-specific fungicides applied at B (50% to 80% bloom), P (prior to cluster closure), V (véraison), and H (pre-harvest). b Amendment and timing: LR=leaf removal by hand applied at TB (trace bloom), PS (just after fruit set [post set]), or V (véraison). GA = gibberellin at 5, 10, or 25 mg/L applied at B (50% to 80% bloom). c Means with the same letter are not significantly different according to Fisher's Protected LSD (P < 0.05). d After 2009, these treatments were dropped from the trial. e 10 mg/L GA was applied from 2007 to 2009, and 25 mg/L was applied from 2010 to 2012