Classification: Basidiomycota, Heterobasidiomycetes, Uredinales.
They are obligate parasites
They are often host specific, but many tree
rusts just go to a genus or part of one.
They may use only one host
during their life cycle or may alternate between two unrelated hosts in
completing life cycle (which is odd considering they are so specific!).
Basidia have 4
cells, but some don't seem to produce basidia and are apparently asexual.
Most have up to 5 spore stages.
The most apparent spore stage for many
rusts is the uredinium. The group
Uredinales is named after this. They are usually numerous rusty-orange
pustules. Makes a good memory device (red uredinium,
There are about 4000 species, far fewer on
||blister rusts; stem, limb and cone
||various dicotyledonous families
rusts related to Cronartium or asexual stages of Cronartium
||apple tribe of Rosaceae (usually)
||Cupressaceae, mainly junipers
||usually no uredinial stage
||pine needle rusts
||various herbaceous plants
||Douglas-fir, larches, hemlocks,
||very diverse genus, infect foliage
and sometimes shoots
Some important rust
|white pine blister rust
||What can I say?
|western gall rust,
pine-pine gall rust
||Peridermium (or Endocronartium)
||Globose galls, spermogonia
uncommon. Decimated plantations like "orange groves."
|eastern gall rust,
pine-oak gall rust
f. sp. banksianae (and other f. sp.)
Virginia and other pines
||Many oaks (dwarf
chinkapin, bur, chestnut, pin, red)
||Galls like those of
western gall rust
f. sp. fusiforme
||loblolly, slash, and
||Many oaks (water,
willow, laurel, etc.
||Spindle shaped ("fusiform")
other 2/3- needle pines
||In east but not common.
Canker l/w only 2-3
||lodgepole, other 2/3-
Indian paint- brush (West), cow wheat (East)
||Cankers long, l/w >
3. In eastern Canada and West as far south as southern California
eastern red cedar
||No uredinial stage. This
one is unique - conifer is the telial host
|pine needle rust
||2/3-needle pines (red,
||goldenrod or aster
in needles, where it can survive 2-3 years
|leaf rust of poplar and
||Most serious on hybrid
poplars; little damage to larch. Telia winter on poplar leaves.