Blister Canker 
57 
Branches were also notched deeply below the point of in- 
oculation. In such cases the fungous growth was always more 
rapid than where the limbs were left intact. 
The effect of cutting off the water and food supply of trees 
has already been discussed. 
The foregoing data all indicate that both anatomical and 
physiological factors are concerned in modifying immunity to 
blister canker. 
METHODS OF CONTROL 
During the fall of 1912 a series of experiments was insti- 
tuted to discover some means of controlling blister canker. 
One method was to cut out the canker. In doing this the 
cankered surface was removed and the discolored wood cut 
away until sound wood one inch deep surrounded the wound. 
Another was to remove the branch on which the canker was 
located. When it was found impracticable to remove the 
branch the canker was cut out. In cutting out a canker where 
too little sound wood surrounded the wound, the branch was 
removed. 
A number of different disinfectants and covers were used 
on both kinds of wounds. They were so arranged that each 
cover would be used with every disinfectant in about the same 
number of treatments. Some wounds were left without covers 
and some without disinfectants. 
A number of trees were pruned heavily at the time the 
cankers were treated while the remainder were left unpruned. 
All treatments were numbered and records were made of 
the location, size, depth of cut (where the canker was cut out) , 
and amount of sound wood between the discolored area and 
the surface of the bark. 
At the end of the first season as indicated in table 15, it 
seemed that a high percentage of the treatments would prove 
effective since the wounds were healing nicely in the majority 
of cases and both trees and foliage appeared healthy. At the 
end of the second season, however, it was apparent that treat- 
ing cankers according to any of the methods used would not 
prove satisfactory. In many instances the disease was visible 
in the bark at one or more points at the margin of the old 
treatment. On examining these treatments it was found that 
the disease appeared in the bark at points in the margin where 
the discolored wood was nearest to the surface at the time 
the treatment was given, or where for some reason the tissues 
