Melampsora medusae

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Melampsora medusae

Kingdom:	Fungi
Phylum:	Basidiomycota
Class:	Urediniomycetes
Subclass:	Incertae sedis
Order:	Uredinales
Family:	Melampsoraceae
Genus:	Melampsora
Species:	M. medusae

Binomial name

Melampsora medusae
Thüm., (1878)

Synonyms

Melampsora albertensis Arthur, (1906)
Uredo medusae (Thüm.) Arthur, (1906)

Melampsora medusae is a plant pathogen that turns host trees' leaves yellowish-orange. It affects mostly the Douglas-fir, western larch, tamarack, trembling aspen, ponderosa, and lodgepole pine trees. Coniferous hosts are affected in late spring through early August, and trembling aspens from early summer to late fall. It is one of only two foliage rusts that occur naturally in British Columbia.^[1]

[edit] Life Cycle

Symptoms usually are contained to a single year on conifers, shedding the affected needles in fall. To survive the winter Melampsora medusae remain as teliospores on the dead leaves of the host, coming back in the spring to be spread by the wind as basidiospores, and infecting new conifers. After about two weeks, aeciospores are produced on the coniferous needles. Those spores serve as inoculum for an infection in live trembling aspen and other poplar trees in another two weeks. Urediniospores are produced on the poplar leaves, where the infection spreads. Winter then comes, and the cycle begins again.