Type: Rust and Smut Fungi; Description: Spermagonia (seen only on artificially inoculated plants) solitary, ellipsoid, orange yellow, up to 0.2 mm in diameter; on yellow spots on needles. Uredinia in groups, often confluent, golden orange, 0.2–0.5 mm in diameter; mainly on the lower surfaces of leaves but some breaking through to the upper surface. Urediniospores obovate to pyriform, 17–26 × 10–16 μm, uniformly echinulate except for a smooth apical spot. Telia roughly circular to oval, golden brown to dark brown, 0.2–0.6 mm in diameter, coalescing into larger irregular shaped masses; mainly on the lower surfaces of leaves. Teliospores rectangular to triangular, 20–50 × 5–16 μm, brown.

Distribution: Northland, Auckland, Coromandel, Waikato, Bay of Plenty, Taranaki, Taupo, Rangitikei, Wanganui, Wellington, Gisborne, Hawkes Bay, Wairarapa, Nelson, Buller, North Canterbury, Mid Canterbury.; 1st Record: Latch (1980).

Significance: Leaf rusts caused by this and other Melampsora species cause premature defoliation in willows and are regarded as important diseases limiting growth of susceptible cultivars. Species cannot be distinguished by gross morphological characters in the field. Natural infection of conifers not known.; Host(s): Spermagonia only on artificially inoculated Larix kaempferi. Uredinia and telia on Salix ×argentinensis, S. babylonica, S. babylonica × annularis, S. babylonica × chilensis, S. burjatica, S. chilensis, S. ×elegantissima, S. fragilis, S. matsudana, S. ×pendulina, S. pentandra.