Type: Foliicolous algae; Description: Thallus polystromatic, subcuticular, roughly circular, greyish white (resembling a powdery mildew) finally becoming greenish orange, composed of irregularly branched and interwoven prostrate filaments; on the upper surfaces of leaves. Erect hairs penetrating through the cuticle, cylindrical, with a bulbous base, reddish brown to orange, 20–130 μm long. Sporangiophores erect, 2–many-celled, developing from the prostrate thallus. Sporangia (1–5) borne slightly obliquely on a short curved stalk, produced from the swollen tip of the sporangiophore, globose to slightly elliptical, 22–43 × 17–26 μm, surface roughened. Zoospores biflagellate. Gametangia not known. Leaf spots roughly circular and wide spreading, greyish white with a pale yellow halo on the upper surface, pale yellow on the lower surface.

Distribution: Northland, Auckland, Coromandel, Waikato, Bay of Plenty, Wanganui, Wellington, Nelson, Marlborough Sounds.; 1st Record: Chapman et al. (1957).

Significance: Very common on Melicytus spp. in northern North Island but causes no damage.; Host(s): Melicytus macrophyllus, M. ramiflorus.