Effect of Early Fruit-Zone Leaf Removal on Canopy Development and Fruit Quality in Riesling and Sauvignon blanc

Abstract

Canopy management is vital for quality winegrape production. During the 2012 and 2013 growing seasons, the timing of fruit-zone leaf removal (FZLR) was evaluated in two commercial vineyard blocks (<i>Vitis vinifera</i> Riesling and Sauvignon blanc) located north of Prosser, WA. Three different timings of manual FZLR were evaluated with a no-removal control. Leaf removal consisted of complete removal of all leaves and lateral shoots in the fruit zone on both sides of the canopy at prebloom, bloom, and four weeks postbloom. Each vine received the same treatment in both years. No negative implications were observed in total fruit set in either year. When leaf removal was performed, regardless of timing, the fruit zone of the canopy had less lateral shoot development and canopy refill than the control. Leaf removal also improved spray coverage in the fruit zone in Riesling, but the effect was related to the timing of leaf removal relative to the timing of the spray. In 2013, prebloom leaf removal significantly reduced Botrytis bunch rot severity in Sauvignon blanc (<i>p</i> = 0.01) below that of the control and four weeks postbloom leaf removal treatments. In 2013, prebloom leaf removal in Riesling increased terpene concentrations in the harvested juice (<i>p</i> = 0.03). In 2012, postbloom leaf removal in Riesling reduced concentrations of acids below those of the prebloom treatment (<i>p</i> = 0.04) in juice.