Brown discoloration of vascular bundles. Disease can be transmitted by pruning tools. Disinfect tools between trees. Avoid injuring living tissue. Don't replant same kind of tree.
Bacteria infect plant via wounds.
Galls occasionally occur on branches or on roots. In spring, yellowish-orange powdery spores are produced in fissures on galls. Prune out infected branches before spores are produced during spring. Chip and dispose of the prunings. Prune out infected branches.