| CANKERS |
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| Black Canker |
| Sooty Bark Canker |
| Cytospora Canker |
| Cryptosphaeria Canker |
| Hypoxylon Canker |
| Atropellis Canker |
Black Canker |
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Host: Aspen 
Symptoms/Signs: Cankers are target shaped with concentric ridges of dead callus. Older cankers typically have a central area of dead wood surrounded by a series of bark calluses. These callused areas may be concentric in outline, but usually are irregularly shaped and ragged in appearance because of the massive callus folds and flaring dead bark. Bark and exposed wood darken, resulting in a black canker. Biology: Ceratocystis fimbriata
can infect through the epidermis of leaf blades, petioles, and young
stems; but trunk wounds are considered to be the primary places
of infection. Several species of beetles have been found to carry
the fungus and are believed to vector it. Infection first appears
as a circular necrotic area on the trunk around a fresh wound or
branch junction. During cambial growth in the spring, the tree forms
a callus at the margins of the canker, which temporarily walls off
infection. The fungus invades the new cambium and
inner bark during the tree’s next dormant season and kills
a new zone of tissue. This process is repeated each year until the
canker, consisting of successive rings of dead bark and wood, is
formed.
Effects: Ceratocystis fimbriata seldom kills large trees since trees generally grow faster in circumference than black cankers enlarge. However, it is possible for several cankers to coalesce and girdle a tree. The greatest damage from this disease is stem deformation and subsequent decay that can result in bole breakage. Similar Insects and Diseases: Sooty bark (Encoelia pruinosa) is also black in color but does not form a target canker like C. fimbriata.
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