Phyllactinia amelanchieris is a species of powdery mildew in the family Erysiphaceae. It is found in North America, where it affects the genus Amelanchier.
The fungus forms a weak, very thin, often smooth coating on the undersides of leaves. P. amelanchieris, like most Erysiphaceae, is highly host-specific and infects only the genus Amelanchier. Another species of powdery mildew also infects this genus: Podosphaera amelanchieris, which forms a thin, light, weak coating on host leaves, rarely distorting growth from the underside.
The fungus was formally described in 2025 by Michael Bradshaw and James Kameron Mitchell.