Weißeln von Obstbäumen zur Vermeidung von Frostrissen und Stamminfektionen mit Pseudomonas syringae

Painting the trunks of deciduous fruit trees white prevents frost injuries. Frost cracks in the bark are important entry sites to the trunk for many plant pathogens such as Pseudomonas syringae, which causes decline of fruit trees. Frost damage and the epiphytic Pseudomonas population on trunks were significantly reduced by painting trees with white paint before the first frost in autumn. A copper compound (Funguran) was added to the paint. This sort of protection from frost injuries relies primarily on the physical effect that the sunlight does not warm the bark, since it is reflected by the white colour. Heating up the bark on the sunny side of the trunk during frost periods leads to tension cracks. A number of products were tested for their stability on bark and their ability to cover trunks and reflect sunlight. Some colours were stable for the whole observation period (more than 100 days) and guaranteed effective heat protection. In conclusion, painting the trunks of deciduous fruit trees white effectively controlled frost cracks. Moreover, the results of a 2-year field trial indicate that trunk infections of Pseudomonas syringae were prevented by using a white paint to which a copper compound was added.