Hi,

I am out of ideas for this one. I collected Salix branches with dark spots on them, and it turned out that on these dark spots there were tiny ascomata of a Wentiomyces-like fungus. It is characterised by branched, dark setae and 3-septate ascospores measuring 11-16 x 4.3-6.0 µm. Asci are bitunicate, a hamathecium is apparently missing.

I am not sure what the larger black spots are on which the fungus is growing. They are reminiscent of old fungal or lichen remains, but I was not able to verify this so far. Sometimes the ascomata were also accompanied by some anamorph (last two photos).

Best wishes,
Gernot