GALL
upperside of the leaves with hollow blisters that may be reddish brown above; their underside bears a layer of microscopical asci that, when fully developed, may give the surface a mealy aspect. Also many-years old witches’ brooms may be formed.
HOST PLANTS
Prunus avium, cerasus, fruticosa, padus.
[click below for photos]
”- Willem N. Ellis: (2021) Plant Parasites of Europe©