Comandra Blister Rust
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Hosts
Lodgepole pine and ponderosa pine are host to both diseases although Stalactiform blister rust is rare on ponderosa pine.
Distribution
Range of hosts in Idaho and Montana. Comandra blister rust is especially severe in south-central Montana. Stalactiform blister rust is generally restricted to high elevations (above about 5,000 feet).
Damage
The fungi cause cankers which eventually girdle branches or sterns resulting in top kill or tree death. Infection is occasionally heavy in stands causing high volume losses.
Identification
Flagged branches have cankers with rough bark and, in late spring, pustules of yellow or orange spores. Stem cankers on young trees or small cankers on larger trees have roughened bark (fig. 22), heavy resin flow, and often insect boring in the killed cambium. With time, stem cankers slough the dead bark at the center. Dead, resinous sapwood is ridged in target form (fig. 23) (concentric ridges of sapwood resulting from annual growth of the canker). Pustules of yellow or orange spores are sometimes produced at edges of stem cankers in early spring. Porcupines and other rodents often chew the bark at canker margins. Large stalactiform blister rust cankers are many times longer than their width. Comandra blister rust cankers are usually 2-5 times longer than wide. The two are best identified by microscopic examination of spores.
Similar damages
Atropellis cankers are also common on lodgepole and ponderosa pines. The sapwood under Atropellis cankers is stained dark blue or black. Rodent chewing at canker margins sometimes results in cankers being overlooked. Concentric ridges of sapwood and dead cambium under nonchewed bark are indicators of cankers.
References
Anonymous. 1982. For. Insect & disease identification and management. USDA For. Serv., Northern Region; Idaho Dept. of Lands, Insect and Disease Control; Montana Dept. of State Lands, Division of Forestry. 192 p.
Bega, R.V. 1978. Diseases of Pacific Coast conifers. USDA For. Serv. Ag. Hndbk. No. 521, 206 p.
Hepting, G.E. 1971. Diseases of forest and shade trees of the United States. USDA For. Serv. Ag. Hndbk. No. 386, 658 p.
Johnson, D.W. 1986. Comandra blister rust. USDA For. Service, For. Ins. & Dis. Leaflet 62, 8 p.
Ziller, W.G. 1974. The tree rusts of western Canada. Can. For. Serv., Publ. No.1329, Dept. of the Env., Victoria, B.C. 272 p.
Field Guide to Diseases and Insect Pests of Idaho and Montana Forests, USDA Forest Service Northern Region, Publication Number R1-89-54
