Nectria cinnabarina (fungus), N. coccinea, N. galligena
Hosts include apple, basswood, black locust, buckthorn, elms, honey locust, maples, oaks, Russian olive, sweet gum, walnut, zelkova, and numerous other hardwoods. N. cinnabarina on larches and jack pine in Ontario, Canada and is found worldwide.
Contributing factors are wounding, improper or untimely pruning, drought, freeze injury. Optimum temperatures 70∞ – 79∞ F.
First apparent by discoloration and sinking of bark surrounding injuries or branch stubs. Affected areas become depressed, with raised, calloused edges; canker may eventually girdle branch or stem. Round, salmon-red pustules (perithecia) scattered about canker; canker perennial, target-type. Premature wilting of foliage in late spring or early summer may accompany canker development; infected wood green to black. In second year, pustules of N. galligena become cream-colored. N. cinnabarina weakly pathogenic, but may invade live wood. Canker growth is slow but significant problem on recent transplants.
The spores invade wounds or branch stubs and germinate in a moist atmosphere in spring; dead wood is invaded where fungus becomes established. Surrounding live wood may be invaded and the bark killed. Fungus becomes established at periphery of dead and live wood. Here new spores are produced in flask-shaped structure (perithecia) and open spordochia to re-infect new wounds and stubs. Spores are airborne or carried in splashing rain.