Fig. 1: Damage caused by Lecanosticta on Swiss mountain pine Pinus mugo ssp. rotundata in the Sindelbacher Filz moor. Photo: Dr. Nicole Burgdorf (LWF)
In many raised bogs in southern Bavaria, our bog or mountain pines (Pinus mugo, subspecies rotundata) are ailing badly or even dying off completely. The reason for this is a fungus that originates from America: Lecanosticta. It causes the brown spot needle blight that is currently afflicting the subspecies of mountain pine Pinus mugo, subspecies “rotundata”, also known as moor or bog pine; and Pinus mugo, subspecies “mugo”, also known as dwarf mountain pine, in the southern Bavarian raised bogs.
Bog pine and dwarf mountain pine are subspecies of the same species, the mountain pine. Mountain pines are usually the most important and sometimes even the only tree species on these moist and acidic extreme sites. The disease is not only spreading among mountain pine in the raised bogs, however, but also in the Alpine valleys, in the upper Isar valley in the Karwendel region, where the source of the River Isar is to be found, and in the Wimbachgries region in Berchtesgaden National Park.
After infection with the Lecanosticta needle blight fungus (Lecanosticta acicola), yellow spots first form on the needles. These then turn brown, and the infected needles die off. The mountain pines become “bald” over time and ultimately, they die. In the case of a severe outbreak, the bog is a shocking sight, displaying the skeletons of many dead trees.
Experts conjecture that the current marked increase in damage could be related to the ever more frequent dry spells and decreasing water levels. Heat waves weaken the mountain pine. Especially in combination with subsequent precipitation, they could lead to mass infections. However, this has not yet been fully investigated. It is therefore also uncertain whether and how the spread can be stopped.
The Bavarian State Institute of Forestry has thus launched a research project to shed some light on the matter. And this is important for the long-term preservation of Bavaria’s mountain pine raised bogs and Pinus mugo protection forests. After all, Bavaria has a special responsibility to protect the mountain pine, since a large part of its globally small range is to be found in southern and eastern Bavaria.
Fig. 2: Mountain pine stripped of their needles in the Wildsteig raised bog. Photo: Eberhard Pfeuffer
Fig. 3: Damage to mountain pine in the Hirtmoos bog near Rottenbuch. Photo: Werner Schubert
