Sunburn in grapes is a damaging symptom that can lead to the berries drying out. The cause and countermeasures do not seem to have been fully clarified, but there is a presumption that too early defoliation of the grape zone of the vine promotes the development of the damage. Berries that have been in the shade for a long time during the growing season and were unable to adapt to the new conditions in time after defoliation are the most sensitive. The sensitivity obviously increases with increasing drought stress .
Classic sunburn on berries shows up in the form of a round spot with burnt skin on the side facing the sun. In extreme cases, the berry skin tears and it dries out.
On the other hand, direct sunlight promotes the formation of quercetin . Quercetin is said to have far-reaching, physiologically positive effects. The anti- carcinogenic effect, which is mainly due to the antioxidant potential , should be emphasized .
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- Karl Bauer et al .: Viticulture . 8th edition 2008, Österreichischer Agrarverlag, ISBN 978-3-7040-2284-4
- Horst Diedrich Mohr: color atlas diseases, pests and beneficial insects on the grapevine . Eugen Ulmer, 2005, ISBN 3-8001-4148-5 .
- Helga Reisenzein, Friedrich Polesny, Erhard Höbaus: Diseases, pests and beneficial insects in viticulture . Österreichischer Agrarverlag, 5th edition, Vienna 2008, ISBN 978-3-7040-2319-3 .
- Heat damage to grapes, sunburn - Rebschutzdienst Lower Austria
- Information page of the German wine analysts ( Memento from October 20, 2007 in the Internet Archive )