Sawadaea bicornis ?

[BubikolRamios]

Checking, nowhere on net to find image like upper side of leafs on this image ...

[abeja]

Hi,
in my opinion no fungus, but galls (caused by mites).
Similar: Aceria macrocheluserinea on Acer (on several species, A. pseudoplatanus mentioned)
https://bladmineerders.nl/en/parasites/ ... luserinea/

Most pictures show the lower side, these white patches are called "erineum" (descriptions see PDF linked below: "felty patches of hairs, also known as filz gall"). Later on they become rosé and brownish. Sometimes upper sides are infected as well.

https://www.naturespot.org/species/acer ... erinea-agg
BUT:

The taxonomy of erineum galls on Acer species is unclear. See British Plant Galls (Redfern & Shirley, 2023) and Buckton, S.J. (2023)
A provisional key to eriophyoid mite erinea on Acer in Britain: https://www.britishplantgallsociety.org ... ea-key.pdf

28 pages ... I didn't read properly.

[BubikolRamios]

Thanks.