Type: Foliicolous Fungi; Description: Conidiomata acervular, scattered, intraepidermal, up to 400 am in diameter; on small (1–2 mm diameter) roughly circular to angular, black leaf spots with whitish centres on both sides of leaves, and on elongate (up to 10 mm long) or circular lesions (3–5 mm in diameter) on young shoots. Conidia obovoid, straight or slightly curved, unequally 1-septate, 11–21 × 4–7 μm, smooth, hyaline. Microconidia sometimes present, ellipsoid, 0-septate, 3–5 × 1–2 μm, hyaline.

Distribution: Auckland, Bay of Plenty, Taupo, Taranaki, Wellington, Hawkes Bay, Mid Canterbury, Dunedin.; 1st Record: Morrison (1977).

Significance: Some clones of Populus deltoides and P. nigra are particularly susceptible to M. brunnea, trees being progressively weakened by repeated premature defoliation. Resistant clones are now used. The disease is not a major problem in New Zealand (Spiers 1998).; Host(s): Populus alba, P. alba × deltoides, P. alba × nigra, P. alba × yunnanensis, P. angustifolia, P. balsamifera × trichocarpa, P. ×canadensis, P. ciliata, P. deltoides, P. deltoides × maximowiczii, P. deltoides × yunnanensis, P. fremontii, P. fremontii × nigra, P. ×generosa, P. koreana × maximowiczii, P. koreana × nigra, P. koreana × trichocarpa, P. lasiocarpa, P. maximowiczii, P. maximowiczii × berolinensis, P. maximowiczii × nigra, P. maximowiczii × trichocarpa, P. nigra, P. simonii, P. szechuanica, P. trichocarpa, P. wilsonii, P. yunnanensis.