Early fruit-zone leaf removal in Eastern Washington: effects on vine development and fruit quality

Brittany Komm

Canopy management is vital for quality wine grape (Vitis vinifera) production. Research has shown that fruit-zone leaf removal (FZLR) improves fruit quality and reduces the severity and incidence of diseases such as powdery mildew (Erysiphe necator) and Botrytis bunch rot (Botrytis cinerea) (BBR). However such aspects are not the only things growers have to look at before implementing cultural practices such as FZLR. Pioneering research has reported significant reductions in fruit set and yield when FZLR was implemented prior to or during bloom. However, many of these studies were conducted in climates cooler than those in eastern Washington. Will the hot, arid climate of eastern WA also realize these outcomes when FZLR is implemented prior to or during bloom? During the growing season of 2012 and 2013, the timing of FZLR was evaluated in two commercial vineyard blocks (V. vinifera 'Riesling' and 'Sauvignon blanc') located north of Prosser, WA. Three different timings of manual FZLR were evaluated relative to a no-removal control. Leaf removal consisted of complete removal of all leaves and lateral shoots in the fruiting-zone on both sides of the canopy at the specified times of pre-bloom, bloom, and four weeks post-bloom. The same leaf removal treatments were applied to the same vines during both v years of the study. For the duration of this study we investigated the horticultural impacts of fruit-zone leaf removal on key horticultural parameters important for grape production in eastern Washington: fruit set, fruit quality (°Brix, TA, pH), canopy development, temperatures within the fruiting-zone, light interception within the fruiting zone, disease and sunburn severity, and cold hardiness. This study found no negative implications on fruit quality and vine development parameters. Positive outcomes seen were, a significant reduction in BBR severity in 2013 Sauvignon blanc (p = 0.02). Reductions in sunburn severity in earlier treatments, (not significant) and significantly increased bud shoot fruitfulness in earlier 2013 Riesling treatments (p = 0.0005). No significant reductions were found in regards to overall cold hardiness or canopy development. Overall, early FZLR in eastern WA may prove to be a viable addition to vineyard management practices.

Early fruit-zone leaf removal in Eastern Washington: effects on vine development and fruit quality

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