Melampsora medusae
Encyclopedia
Melampsora medusae is a fungal
pathogen
, causing a disease of woody plant
s. The infected trees' leaves turn yellowish-orange. The disease affects mostly conifers, e.g. the Douglas-fir
, western larch
, tamarack
, ponderosa
, and lodgepole pine
trees, but also some broadleaves, e.g. trembling aspen
and poplars. Coniferous hosts are affected in late spring through early August, and trembling aspens and poplars from early summer to late fall. It is one of only two foliage rusts that occur naturally in British Columbia
.
s on the dead leaves of the host, coming back in the spring to be spread by the wind as basidiospore
s, 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. Urediniospore
s are produced on the poplar leaves, where the infection spreads. Winter then comes, and the cycle begins again.
Fungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...
pathogen
Pathogen
A pathogen gignomai "I give birth to") or infectious agent — colloquially, a germ — is a microbe or microorganism such as a virus, bacterium, prion, or fungus that causes disease in its animal or plant host...
, causing a disease of woody plant
Woody plant
A woody plant is a plant that uses wood as its structural tissue. These are typically perennial plants whose stems and larger roots are reinforced with wood produced adjacent to the vascular tissues. The main stem, larger branches, and roots of these plants are usually covered by a layer of...
s. The infected trees' leaves turn yellowish-orange. The disease affects mostly conifers, e.g. the Douglas-fir
Douglas-fir
Douglas-fir is one of the English common names for evergreen coniferous trees of the genus Pseudotsuga in the family Pinaceae. Other common names include Douglas tree, and Oregon pine. There are five species, two in western North America, one in Mexico, and two in eastern Asia...
, western larch
Western Larch
Western Larch is a species of larch native to the mountains of western North America, in Canada in southeastern British Columbia and southwestern Alberta, and in the United States in eastern Washington, eastern Oregon, northern Idaho and western Montana.It is a large deciduous coniferous tree...
, tamarack
Tamarack Larch
Tamarack Larch, or Tamarack, or Hackmatack, or American Larch is a species of larch native to Canada, from eastern Yukon and Inuvik, Northwest Territories east to Newfoundland, and also south into the northeastern United States from Minnesota to Cranesville Swamp, West Virginia; there is also a...
, ponderosa
Ponderosa Pine
Pinus ponderosa, commonly known as the Ponderosa Pine, Bull Pine, Blackjack Pine, or Western Yellow Pine, is a widespread and variable pine native to western North America. It was first described by David Douglas in 1826, from eastern Washington near present-day Spokane...
, and lodgepole pine
Lodgepole Pine
Lodgepole Pine, Pinus contorta, also known as Shore Pine, is a common tree in western North America. Like all pines, it is evergreen.-Subspecies:...
trees, but also some broadleaves, e.g. trembling aspen
Populus tremuloides
Populus tremuloides is a deciduous tree native to cooler areas of North America, commonly called quaking aspen, trembling aspen, American aspen, and Quakies,. The trees have tall trunks, up to 25 metres, with smooth pale bark, scarred with black. The glossy green leaves, dull beneath, become golden...
and poplars. Coniferous hosts are affected in late spring through early August, and trembling aspens and poplars from early summer to late fall. It is one of only two foliage rusts that occur naturally in British Columbia
British Columbia
British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
.
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 teliosporeTeliospore
Teliospore is the thick-walled resting spore of some fungi , from which the basidium arises.-Development:They develop in telia ....
s on the dead leaves of the host, coming back in the spring to be spread by the wind as basidiospore
Basidiospore
A basidiospore is a reproductive spore produced by Basidiomycete fungi. Basidiospores typically each contain one haploid nucleus that is the product of meiosis, and they are produced by specialized fungal cells called basidia. In grills under a cap of one common species in the phylum of...
s, and infecting new conifers. After about two weeks, aeciospores are produced on the coniferous needles. Those spores serve as inoculum
Inoculation
Inoculation is the placement of something that will grow or reproduce, and is most commonly used in respect of the introduction of a serum, vaccine, or antigenic substance into the body of a human or animal, especially to produce or boost immunity to a specific disease...
for an infection in live trembling aspen and other poplar trees in another two weeks. Urediniospore
Urediniospore
Urediniospores are the thinner-walled spores of some fungi: , from which the basidium arises.-Morphology:*Urediniospores are usually consist of two dikaryote nuclei within one constricted cell resembling the number 8 without a septation...
s are produced on the poplar leaves, where the infection spreads. Winter then comes, and the cycle begins again.