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Genetic Variation in Disease Resistance of Native Forest-Tree Species

Forest-tree diseases may be classified in many ways but for the purpose of this discussion I should like to separate them into two groups, those that can operate only when tree vigor is reduced and those that can and do operate regardless of tree vigor. In both groups the severity of the disease depends upon the interaction of two factors, the virulence of the pathogen and the resistance of the host to successful attack. In the first group, however, the resistance of the host can be increased by cultural practices that raise the vigor of individual trees and stands, whereas in the second group the only method of increasing individual tree resistance in a stand is to weed out the susceptible trees and replace them with trees that are resistant. This basic distinction should be the deciding factor in determining the type of control program recommended for any disease. For diseases that are dependent upon reduced tree vigor from whatever cause, control should be secured by improving cultural practices or by growing the crop on sites and in geographic locations where the tree species is most vigorous.


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Author(s): J. R. Hansbrough

Publication: Tree Improvement and Genetics - Northeastern Forest Tree Improvement Conference - 1953