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Defoliation

defoliation (GB)

This measure (also leaf pruning, summer pruning) in the vineyard is carried out several times if necessary. A limited number of leaves are removed from the grape zone. The measure is recommended for short-shooted, densely-leaved grape varieties with compact, densely-berried grapes and thin berry skins, for example Pinot Noir, Gewürztraminer, Kerner, Müller-Thurgau and Scheurebe (seedling 88). Defoliation favours air circulation in the grape zone, so that the grapes dry much faster after rain. This protects the ripening fruit from premature botrytis attack. Defoliation begins two to three weeks after flowering, but not too many leaves should be removed, because until the véraison (start of ripening) the green berries are still at high risk of sunburn.

Entbläötterung - maschinell (ERO)

Shading

Shading with dense foliage is very effective in protecting against intense sunlight and the resulting grape wilt. In August to mid-September, however, individual leaves are also removed, thus improving the air and light conditions. This also counteracts grape rot and also leads to better colour formation in red wine grapes. Today, defoliation is also carried out mechanically in large wineries. However, defoliation should not be too severe, because a sufficient number of healthy leaves is important for photosynthesis and sugar production.

Leaf/fruit ratio

An unfavourable ratio between fruit and foliage is reflected in a reduced content of glucose (grape sugar) and phenols in the must and can possibly impair the wine quality. In addition, external circumstances such as hail or frost, pests such as grasshoppers or vine diseases such as downy mildew can lead to unexpected loss of foliage during the vegetation cycle. The vine reacts to too much loss of foliage by sprouting stingy sh oots (secondary shoots). In the process, carbohydrate reserves are first used up. Extreme, repeated defoliation can lead to death. A unit of measurement for the vigour or yield capacity of a vine is the cut wood weight. Low amounts of wood indicate weak growth, yield overload, poor leaf/fruit ratio and stress problems.

Leaf fall

Towards the end of the vegetative cycle in late autumn, when the vine has replenished its reserve of carbohydrates, leaf fall occurs. This natural process usually occurs with the first frost. Complete defoliation by means of chemical agents shortly before the grape harvest in order to facilitate mechanical harvesting is not expedient. This is because after the harvest until the natural leaf fall, the foliage still contributes considerably to the good maturation of the one-year-old shoots and to the storage of reserve substances in the vine. See also under Pruning and under Vineyard Care.

Picture: ERO GmbH

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