Tree cankers are defined as localized rigions of necrosis in the bark of stems or branchs. The infectious diseases are mainly caused by facultative fungi, occassionally by bacteria, and usually found in conifers and hard woods. Damages from small depressions in the outer bark to a rapid girdding of the branchs and stems with high mortality occur consequently. On the basis of authors’ recent investigations the symtoms, pathogens, paths and seasons of infection, host resistance, environmental conditions affecting disease development and control of the tree cankers were generally discussed. The symptom of the tree cankers developed usually in the early spring when host plants were weakened by adverse enviromantal factors such as drought, frost, unfavorable soil conditions, mismanagement,insect damage etc. Intensively silviculture managements can promote the growth vigor of trees that is commonly known as an economic and effective measure to prevent the infection of tree cankers. In the cases of trees infected with various initial lesions, treatments with fungicides are advisable.