Cytospora Canker - Field Guide to Diseases and Insect Pests of Idaho and Montana Forests

Cytospora Canker

Cytospora abietis Sacc., C. kunzei Sacc.

From: Field Guide to Diseases and Insect Pests of Idaho and Montana Forests, USDA Forest Service Northern Region, Publication Number R1-89-54

Hosts. – Cytospora abietis--True firs and Douglas-fir are most often attacked although western hemlock and western redcedar are occasional hosts.

Cytospora kunzei (Leucostoma kunzei (Fr.) Munk. – Spruce and Douglas-fir.

Distribution. – Range of hosts in Idaho and Montana.

Damage. – Branch and stern cankers are produced. Branches are quickly girdled and killed as are tops of seedlings. Stem cankers occasionally girdle and kill saplings, seldom larger trees.

Identification. – Flagged branches and dead tops of seedlings and saplings are usually the most obvious symptoms (fig. 24). Sunken bark with dead cambium underlying is the result of the canker. If the edge of the canker is cut with a knife, an abrupt margin is observed between the green, live bark and the brown, dead bark (fig. 25). Slight resin flow is often present at the canker margin and the bar k within the cankered area often appears discolored (fig. 26). Sporulation is seldom observed. Orange tendrils of spores exude from microscopic holes in the bark at canker margins.	Image Unavailable
	Figure 24 - Cytospora Cankers usually occur on branches causing branch flagging.
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Figure 25 - Cankers can be easily diagnosed by cutting away the bark. An abrupt margin is seen between dead and live cambium.	Figure 26 - Cytospora occassionally causes cankers in larger stems.

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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.

Boyce, J. S. 1961. Forest Pathology. McGraw-Hill Book Co., New York, NY. 572 p.

Funk, A. 1981. Parasitic microfungi of western trees. Canadian Forestry Service, Pacific Forest Research Centre BX-X-222, 190 p.

Hepting, G. E. 1971. Diseases of forest and shade trees of the United States. USDA For. Serv. Ag. Hndbk. No. 386, 658 p.

Scharpf, R. F. and H. H. Bynum. 1975. Cytospora canker of true firs. USDA For. Serv., For. Pest Leaflet 146, 5 p.

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