I think the white (there were many like this) were caused by the weather. Please let me know if you think otherwise.
Wearing a superhero mask.
On Helliborus (Christmas rose)
IN Europe, othe species are also noted, such as Coniothyrium delacroixii and Coniothyrium olympicum.
According to the USDA Mycological Herbarium database:
https://nt.ars-grin.gov/fungaldatabases/specimens/new_frameSpecimenReport.cfm
I'm not very happy with this ID becuase I can not find any info on the cell or leaf sizes of this species.
Leaves are .75 x .25, medial cells average 30X5. Growing on a big leaf maple tree next to a river. There was not much of it there so maybe this is not a very good sample.