Classification: Basidiomycota, Heterobasidiomycetes, Uredinales.
They are obligate parasites
and biotrophs.
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,
Uredinales).
There are about 4000 species, far fewer on
trees.
Some important
genera
| Genus |
Common Name |
Aecial Hosts |
Telial Hosts |
Comments |
| Cronartium |
blister rusts; stem, limb and cone
rusts |
pines |
various dicotyledonous families |
|
| Peridermium |
|
|
|
asexual
rusts related to Cronartium or asexual stages of Cronartium
spp. |
| Gymnosporangium |
|
apple tribe of Rosaceae (usually) |
Cupressaceae, mainly junipers |
usually no uredinial stage |
| Coleosporium |
pine needle rusts |
pines |
various herbaceous plants |
|
| Melampsora |
|
Douglas-fir, larches, hemlocks,
others |
poplars, willows |
very diverse genus, infect foliage
and sometimes shoots |
Some important rust
diseases
|
Pathogen |
Aecial Host |
Telial Host |
Comments |
| white pine blister rust |
Cronartium ribicola |
5-needle pines |
Ribes spp. |
What can I say? |
| western gall rust,
pine-pine gall rust |
Peridermium (or Endocronartium)
harknessii |
2/3-needle pines |
probably none |
Globose galls, spermogonia
uncommon. Decimated plantations like "orange groves." |
| eastern gall rust,
pine-oak gall rust |
Cronartium quercuum
f. sp. banksianae (and other f. sp.) |
jack, shortleaf,
Virginia and other pines |
Many oaks (dwarf
chinkapin, bur, chestnut, pin, red) |
Galls like those of
western gall rust |
| fusiform rust |
Cronartium quercuum
f. sp. fusiforme |
loblolly, slash, and
other pines |
Many oaks (water,
willow, laurel, etc. |
Spindle shaped ("fusiform")
galls |
| comandra rust |
Cronartium comandrae |
lodgepole, ponderosa,
other 2/3- needle pines |
comandra (herbs) |
In east but not common.
Canker l/w only 2-3 |
| stalactiform rust |
Cronartium
coleosporioides |
lodgepole, other 2/3-
needle pines |
Scrophulariaceae e.g.
Indian paint- brush (West), cow wheat (East) |
Cankers long, l/w >
3. In eastern Canada and West as far south as southern California |
| cedar-apple rust |
Gymnosporangium
juniperi-virginianae |
apple |
junipers, especially
eastern red cedar |
No uredinial stage. This
one is unique - conifer is the telial host |
| pine needle rust |
Coleosporium
solidaginis |
2/3-needle pines (red,
jack, Scots) |
goldenrod or aster |
Overwinters
in needles, where it can survive 2-3 years |
| leaf rust of poplar and
larch |
Melampsora medusae |
larches |
poplars |
Most serious on hybrid
poplars; little damage to larch. Telia winter on poplar leaves. |
|