Hosts: Ponderosa and Mondel pines (Pinus
eldarica), and Comandra pallida is the alternate host.
Figure 228. Comandra pallida with leaf infections.
Symptoms/Signs: Symptoms of disease on pine begin with slight, spindle-shaped
swellings that give rise to pustules that soon exude a mass of rust
colored spores. On the nonnative Mondel/Eldarica pine, comandra
blister rust causes dieback of branches and eventual tree death.
On ponderosa pine, its native host, this disease is rare but occasionally
girdles seedlings and saplings. On Comandra pallida, the
native alternate host, the rust causes pale yellow leaf and stem
spots and leaf abscission.
Figure 229. Comandra blister rust swollen canker.
Biology: The aecial stage develops on pine in late spring through early
summer and spores disseminate by wind at that time. These spores
are responsible for the primary infection of the alternate host,
C. pallida. Rain and cool temperatures favor their germination.
The next spore stage, the so-called repeating stage, occurs and
builds up on Comandra, as long as there is wet weather. The final
stages give rise to basidiospores in late summer, which are wind-dispersed
to infect pine needles. The fungus grows into the inner bark, forming
a canker that eventually girdles the branch or stem.
Effects: Although this disease causes major
damage to lodgepole pine and sometimes ponderosa pine in northern
Colorado and Wyoming, it is of minor consequence to ponderosa pine
in Arizona and New Mexico. However, Comandra blister rust has done
considerable damage to plantings of Mondel pine in the Prescott,
Sedona and Payson areas of Arizona. Beginning in the late 1970s,
Mondel pines were planted widely as a landscape tree throughout
these areas, until it was realized that Comandra blister rust impacted
their survival. Infected C. pallida are typically observed
near infected Mondel pines.