GALL
leaves much broader than normal, reddened to bluish-purple; the shoots are somewhat enlarged; usually the galling concerns isolated shoots. The spores are curved, septate, up to 18 µm long.
HOST PLANTS
Ericaceae, monophagous: Andromeda polifolia.

[click link below for photos]

- Willem N. Ellis: (2021) Plant Parasites of Europe^©

Reference: https://bladmineerders.nl/parasites/fungi/dikarya/basidiomycota/ustilaginomycotina/exobasidiomycetes/exobasidiales/exobasidiaceae/exobasidium/exobasidium-karstenii/