Exobasidium vaccinii (Fuckel) Woronin, 1867
cowberry redleaf, azalea leaf and flower gall
on Vaccinium
Vaccinium vitis-idaea, France, dép. Haute-Loire, Chanaleilles, mnt La Garde au Truc, 1380 m © Henri Maleysson: at rare occasions also a flower becomes galled
the calling mainly concerns the peduncle and receptacle.

Vaccinium vitis-idaea, estate Tongeren © Hans Jonkman

Vaccinium vitis-idaea, Tongeren, het Greveld © Arnold Grosscurt

another type of this gall

upperside of the same leaf
gall
The spores are slender, curved, up to 19 µm long, septate.
host plants
Ericaceae, narrowly monophagous
Vaccinium vitis-idaea.
Redfern & Shirley associate the fungus also with Empetrum nigrum. Given the extreme monophagy in the genus Exobasidium, this is hard to believe. Perhaps Exobasidium empetri Ito & Otani, 1958 does occur in Scotland?
references
Begorow, Bauer & Oberwinker (2001a), Bellmann (2012a), Blumer (1946a), Buhr (1964b), Dauphin & Aniotsbehere (1997a), Döring (2003a), Doppelbaur (1973a), Ing (1994a, 2001a), Coulianos & Holmåsen (1991a), Klenke & Scholler (2015a), Koops (2013a), Kozłowska, Mułenko & Heluta (2015a), Kruse (2019a), Mervielde (2001a), Pellicier (2001a), Negrean (1996b), Redfern & Shirley (2011a), Roskam (2009a), Schmid-Heckel (1985a), Spooner (1988a), Tomasi (2003a), Woods, Chater, Smith ao (2018a).