Stalactiform blister rust, Cronartium coleosporioides,

Fig. 166 Blisters contain orange spore masses. Note stripped bark due to squirrel feeding.	Fig. 167 Elongated stem canker.	Fig. 168 Branch canker infection.

Distribution: Throughout B.C.

Host Susceptibility:  The primary hosts are lodgepole and ponderosa pine. Alternate hosts include Indian paintbrush (Castilleja spp.) and other species of the figwort family (Scrophulareacea).

Signs & Symptoms: Trees of all ages can be infected but mortality occurs primarily on small or slow-growing trees. The fungus is an obligate parasite and the host often does not show crown symptoms until just before death. The disease causes a bark canker which is often lethal when located on the stem. Cankers appear as elongated swellings that slowly girdle the branch or stem. Cankers are diamond-shaped and typically 10 times higher than wide. Stem cankers can be several metres in length. In the spring, blisters appear and release orange spores which infect the alternate host. Spores returning from the alternate host infect pine needles in the late summer.

Damage: Mortality occurs rapidly on very young trees. Due to the slow growth of stalactiform cankers, large infected trees will survive to a commercial thinning or harvest but will suffer increment loss and reduced wood quality. Canker edges are often fed upon by squirrels. Repeated feeding on cankers can result in a striated pattern of bark stripping. Spike tops on older trees result when live crown exists below the canker.

Can Be Confused With:  Stalactiform blister rust can be confused with atropellis canker and other pine stem rusts, such as sweet-fern blister rust and comandra blister rust. Stalactiform branch cankers are narrow, elongated, and pointed, whereas comandra cankers are blunt-ended. Stalactiform canker height is at least 10 times the width (elongated), whereas comandra stem canker height is only 1.5 times the width (diamond-shaped). Atropellis cankers are never fed upon by squirrels and contain black-stained wood directly beneath the canker. 

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Contact Tim Ebata if you have comments on the presentation of this information.

BC Ministry of Forests
Forest Practices Branch
P.O. Box 9513 Stn. Prov. Gov.
Victoria, BC
V8W 9C2

Section phone: (250) 387-8739
Section fax: (250) 387-2136

Last updated April 23, 2002