Comandra blister rust

French disease name: Rouille - tumeur oblongue
Pathogen name: Cronartium comandrae Peck
Kingdom: Fungi
Phylum: Basidiomycota
Class: Pucciniomycetes
Order: Pucciniales
Family: Cronartiaceae
Partial list of synonyms:
- Cronartium asclepiadeum (Willd.) Fr. var. thesii Berk.
- Cronartium pyriforme Hedgc. & W.H. Long

Distribution

Canada

Damage, symptoms and biology

Trees of all sizes and ages are affected, and the presence of cankers can result in growth defects and mortality. Outbreaks of this disease are sporadic, due to variations in the distribution of the alternate host and the periodicity of environmental conditions necessary for infection. The most serious damage has been observed in nurseries and plantations where rapid stem girdling results in high mortality.

A large numbers of galls reduces the aesthetic appearance and value of ornamentals and Christmas trees.

Other information

The aecial cankers of comandra blister rust are very similar in appearance to those of sweet-fern and stalactiform rusts. However, examination of the uniquely shaped aeciospores with a microscope or even a hand-lens will distinguish this rust from others. Swellings on seedlings might be confused with pre-sporulating gall of Endocronartium harknessii; however, C. comandrae swellings result from swollen bark, while E. harknessii galls have normal bark over abnormally thickened xylem tissue.