Aceria epiphyllus ?
Not related to Ash die back.
No identification made yet.
No interactions present.
Not sure that this is a gall at all. If it is it is not Aceria epiphyllus (which by the way is now Aculus epiphyllus). It might just be Dasineura fraxinea (a midge) but I am very doubtful.
Is it worth pursuing, or maybe that should read, will it be...? Seriously, I do have 2 common Ash trees in my gardens,* (albeit bonsaied) not infected, (so far), by "Ash die back". A dodgy future for them both, time will tell....
Thanks For your comment Peter, all noted.
* 1 in the back and 1 in the front, in the ground not in pots.
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