Forum Flora Germanica

Hi,
I don't think this is Puccinia (any stage), nor a rust fungus at all.

It resembles a pyrenomycetous fungus. Is there any elevated crest with a slit-like opening developping in the middle of the black spot? (Looking at the small picture ... could be ...)
In my “big book” I stumbled over the genus Lophiostoma.
Lophiostoma macrostomum ("an inmersed black bitunicate, pyrenomycetous fungus with a slit-like ostiole on a raised crest) is growing on herbaceous stems and wood of deciduous trees.
There are similar species with different spores (so micro-features would be necessary), growing in slightly different habitat (on grass/ on wood).
http://ascofrance.com/forum/14094/lophi ... acrostomum

I had a play with direction of light.... There is a longitudal slit almost on any black dot.
If you can see anyhing more... Cnecked other dry stems around. Limited to Paeonia.
http://agrozoo.net/jsp/Galery_one_image ... 435083de42

Hi, I am far from sure about this. We see a slit, but hardly any elevation. Maybe you have the chance to observe a possible development?

On the other hand, I did not find anything in plant pathogens (in living plants) that looks similar. These are often irregular leaf spots.
https://bladmineerders.nl/?s=paeonia

Lophodermium paeoniae

https://www.google.com/search?q=Lophode ... =886&dpr=1

Good idea!
This is quite rare in Germany, I never heard about a Lophodermium spec. on paeonia before.
But in the BMG-Forum ...
https://forum.pilze-bayern.de/index.php?topic=1750.0

(Edit: Lophoderma in Lophodermium geändert)

I guess if you have not woody paeonia dead stems near by, you should find it, it is is all around. At least here.

In the Bavarian forum they were asking people to look for this fungus at garden plants. But here it is very common to remove the old parts. Mostly this fungus was found in one part of Bavaria (Franken), there are spots with paeonia offic. in nature (gone wild or deliberately planted there.)

Just a note, encountered Hypoderma, looks similar:
http://www.dorsetnature.co.uk/pages-fungi/f-225.html
https://fungi.myspecies.info/all-fungi/hypoderma-rubi

They belong to the same family (Rhytismataceae) or at least to the same order (Rhytismatales).
Sometimes it is not yet clear, where to put a genus ... genetics.

Rhytismataceae
https://www.mycobank.org/page/Name%20de ... page/93068

I think the "best-known species" that nearly everyone has seen in passing is Rhytisma acerinum, those black spots on maple leaves.
Here I once managed to see the apothecia break open in spring (found an old leaf, put it into a box at home with some moist paper).
https://forum.dgfm-ev.de/thread/2018-rh ... an-spitza/