See:
Honey Locust (Gleditsia spp.) - Canker
Note: The disease occurs in PNW nurseries, and the cultivar Purple Robe is susceptible. In Europe, several Fusarium spp. have been found. Fusarium sulphureum and F. avenaceum caused cankers (necrosis in living bark and phloem) on stem and twigs without wounding.
Reference Halász, G. 2002. Canker and wilt of black locust (Robinia pseudoacacia L.) caused by Fusarium species. Acta microbiologica et immunologica hungarica, 49:249-260.