During the last three years, many trees have shown an increased development of phloem nodes (small bulbous protrusions on the bark). Despite a three-year study in which the structure and development of phloem nodes were analyzed in detail, the cause has yet to be found. At this time, about 22 % of all broadleaf trees in public spaces in the municipality’s urban region display these phloem nodes. The study revealed three kinds of phloem nodes, all of which display two similar abnormalities: cell necrosis and growth disturbances. This damage is worrisome.
Despite two years of study by the University of Wageningen in the Netherlands, the cause of phloem nodes has not been found.
It has been postulated that the malformations in the bark is related to changes in the environment, such as the ever increasing electromagnetic fields or air pollution. There is now an urgent need for further research on this topic.