Type: Foliicolous algae; Description: Thallus polystromatic, at first subcuticular, roughly circular, appearing as greyish to brownish spots, later penetrating the mesophyll and growing in the vicinity of stomata in the lower epidermis, composed of irregularly branched, lobed and interwoven prostrate filaments; on both sides of leaves. Erect hairs penetrating the cuticle, produced in clusters, tapering, orange, 25–45 μm long, predominantly on the upper surfaces of leaves. Sporangiophores erect, 4–11 cells long, produced in tufts of 3–10 from filaments in the vicinity of stomata and destroying the structure of the stomatal area. Sporangia borne singly on a short curved stalk, which develops from the swollen tip of the sporangiophore, globose, 17–18 µm in diameter, smooth. Zoospores biflagellate. Gametangia sessile, globose to pyriform, 25–50 × 25–35 μm, produced on subepidermal filaments on both surfaces of leaves. Leaf spots on the upper surface circular to oval, dark reddish brown to purple with a purple black margin, 5–25 mm in diameter; on the lower surface golden yellow with tufts of sporangiophores.

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

Significance: Causes considerable damage to tropical fruit trees but of little importance in New Zealand. Very common and conspicuous on leaves of Knightia excelsa.; Host(s): Beilschmiedia tawa, Knightia excelsa, Metrosideros excelsa.