Rust diseases are caused by fungi in the Basidiomycetes, and are obligate
parasites of leaves, bark, flowers. The most serious rusts in timber production
terms are the stem rusts.
Cronartium coleosporioides Stalactiform
Host: lodgepole pine, Indian Paint brush
Damage: causes long sunken, resinous lesions, easily confused
canker from a distance. Can cause mortality and can grow from branch to
Note: Cronartium rust cankers are often found in association
with the Western
pine moth(Dioryctria cambiicola) and the Sequoia
pitch moth (Synanthedon sequoiae.
C. comandrae Commandra blister rust
Host: lodgepole pine, Bastard Toad flax
Damage: causes shorter, wider cankers than stalactiform rust,
otherwise is very similar.
C. comptoniae Comptonia rust
Host: lodgepole pine, Myrica gale
Damage: more frequently a branch rust, but can be similar to
Cronartium ribicola White pine blister rust
Host: soft, or 5-needle pines
Damage: introduced from Asia, has eliminated white pine as a
commercially viable species in North America.
Endocronartium harknessii Western
Host: lodgepole pine
Damage: No alternate host, causes woody galls on branches, stem
infections must have originated on 1-year-old stem, cannot grow from branch
to stem. Can be a sight for breakage, decay.
Melampsora occidentalis Melampsora rust
Host: Douglas-fir (aecial), cottonwood (uredial)
Damage: little on D-fir, some loss of photosynthetic capacity
M. medusae melampsora rust
Host: Douglas-fir (aecial), aspen (uredial)
Damage: as above
Pucciniastrum epilobii fir-fireweed rust
Host: True firs (aecial), fireweed (uredial)
Damage: loss of photosynthetic area with fir.
Chrysomyxa ledicola Large-Spored Spruce-Labrador Tea Rust
Host: aecial hosts: white, black, Sitka, and Englemann spruce.
telial hosts: Labrador-tea and northern Labrador-tea
Damage: Severe defoliation of spruce in localized area. Enhanced
by moist environmental conditions.
Chrysomyxa arctostaphylli spruce broom rust
Host: Spruce (aecial), Arctostaphylos uva-ursi (uredial)
Damage: unsightly brooming, little damage caused otherwise
Melampsora caryophyllacearum fir broom rust
Host: true firs (aecial), chickweed (uredial)
Damage: can cause a decrease in growth of fir if severe enough.
Chrysomyxa pirolata C. monesis spruce cone rusts
Host: spruce, wintergreen (Pirola)
Damage: can destroy cone crops in seed orchards.
Diagrammatic representation of infection structures produced by rust
fungi during the invasion of host plant leaves.