Comandra blister rust, Cronartium comandrae
 

Fig. 163 Diamond-shaped stem canker.	Fig. 164 Canker girdling host stem. Note white blisters, which contain yellow-orange spores.	Fig. 165 Rough bark and resin flow are associated. Note swollen bark at canker margin.

Distribution: Throughout B.C. especially in the SBS biogeoclimatic zone.

Host Susceptibility:  The primary hosts are 2- and 3-needle pines, including lodgepole and ponderosa pine. Alternate hosts include Comandra spp. or Geocaulon spp., primarily bastard toadflax (G. lividum).

Signs & Symptoms: Comandra blister rust is primarily a disease of young lodgepole pine. The fungus is an obligate parasite and the host often does not show crown symptoms until just before death. Most stem cankers are lethal, occurring within 1 m of the ground and often beginning as branch infections. Branch cankers appear as blunt-ended swellings that girdle the branch, whereas stem cankers are oval or diamond-shaped. For most of the year cankers are inconspicuous. 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. Lower branches should be carefully inspected for cankers.

Damage: Most tree mortality occurs between ages 5 and 30. The uneven distribution of mortality often leads to stand gaps. Squirrels commonly feed on cankers and may hasten host mortality. On ponderosa pine, infection occurs on trees of all ages. Spike tops on older trees result when live crown exists below the canker.

Can Be Confused With:  Comandra blister rust can be confused with atropellis canker and other pine stem rusts, such as sweet-fern blister rust and stalactiform blister rust. Comandra branch cankers are blunt-ended, whereas stalactiform cankers are narrow, elongated, and pointed. Comandra stem canker height is only 1.5 times the width (diamond-shaped), whereas stalactiform canker height is at least 10 times the width (elongated). 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 February 18, 2002