Hello.
A suspected Hymenoscyphus sprouting on a thin blueberry (Vaccinium) stem.
Apothecia barely 1 mm in diameter and 1.6 mm high, whitish in color with a blackish base.
Stem hyphae arranged parallel to each other, with brown intracellular pigment.
Marginal hairs with rounded tips and short septa.
Hyphae of the excipulum with an intricate texture.
Octosporous asci, with a very slight amyloid reaction to Melzer's reagent in their tiny apical apparatus. Filiform paraphyses that protrude very slightly above the level of the asci. Ascospores between cylindrical and fusiform, with one pointed end and the opposite end more rounded, containing numerous lipid droplets, and with the following measurements of mature spores free in water:
(18.2) 19.8 - 22.4 (23.6) × (4.5) 4.7 - 5.9 (6.2) µm
Q = (3.1) 3.4 - 4.6 (5.1) ; N = 40
Me = 21.1 × 5.3 µm ; Qe = 4
Based on its characteristics and following the keys (which we cannot name), I am led to believe it is Hymenoscyphus vacini, apparently only associated with Acer, although it does not appear in the keys. Then we also have the very similar Hymenoscyphus fraxineus, apparently associated with Fraxinus, a species I have already studied once and whose presence on Vaccinum I am unsure of.
Any opinions you may have would be greatly appreciated.

Thank you in advance.
Best regards.