Melampsora medusae von Thümen, 1878
on Abies, Larix, Picea, Pinus, Pseudotsuga
not yet found in Europe.
urediniospores pear-shaped, spinulose, but with a smooth zone near the equator; here often the wall pf the spore is somewhat thickened.
Populus balsamifera, carolinensis, nigra & var. italica, tremuloides.
North American species, found at some occasions in mostly southern Europe. In France it is a quarantaine species (Wikipedia, 2016a).
Brandenburger (1985a: 38), European and Mediterranean Plant Protection Organization (2009a), González-Fragoso (1922a, 1925a), Klenke & Scholler (2015a), Vialle, Frey, Hambleton, Bernier & Hamelin (2011a).