This measure in the vineyard primarily serves to increase the quality of healthy grapes and, as a side effect, to reduce the yield. It is especially recommended in the case of a dense and compact grape structure, which can be the cause of grape rot (sour rot). In dense grapes, the interior is poorly ventilated, so that after precipitation (rain, dew) the grapes dry out too slowly and the moisture provides ideal conditions for rot pathogens. In addition, the high pressure in the central part causes berries to be crushed, thus creating the conditions for bacteria and fungi to penetrate. Berries affected by rot lead to wine defects in taste. Grape varieties with compact versus loose berries are particularly at risk; these include Pinot varieties, Sauvignon Blanc, Elbling and Riesling. Various measures have therefore been developed to loosen up the grapes. These include defoliation of the grape zone, as well as grape splitting and grape breaking.
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