Mistletoe is increasingly attacking pine trees in Bavaria’s forests, and an increasing infestation of deciduous trees has been documented in Berlin. Experts in Bavaria are worried about the development because the semi-parasites are further weakening the conifers that are stressed by global warming. “In times when it is dry, it becomes twice as difficult for the tree,” explains Hans-Joachim Klemmt from the Bavarian State Institute for Forestry and Forestry (LWF) in Freising.

In northern Bavaria, experts now want to investigate how infected pine trees are doing and whether mistletoe spread patterns can be identified. Pine trees are mainly found in the north of the Free State. In 2007, the infestation with mistletoe was documented for the first time during the forest status survey, says Klemmt. At that time, 1.7 percent of the sample trees were infected; now it is almost 40 percent. He attributes the increase to global warming. “The living conditions for the mistletoe are getting better. The more severe frosts in winter are no longer there,” says Klemmt.

Since the 1980s, Berlin has been recording mistletoe infestations of deciduous trees such as maple, birch, linden and poplar in selected locations in the southwest of the city. Here too, experts are recording a significant increase in the number of populated trees.

Mistletoe (Viscum album) is known to many people as a Christmas decoration, lucky charm or medicinal plant. According to Klemmt, three species are native to this country: pine mistletoe, fir mistletoe and deciduous mistletoe. Mistletoe removes water and nutrients from the host tree. According to the Nature Conservation Association of Germany (Nabu), birds like to snack on the white berries, which are so sticky that parts stick to their beaks. If they then sharpen their beak on a tree or leave their droppings there, mistletoe seeds stick to the bark.