Blight Canker of the Apple Tree. 



185 



The cankers vary in size from half an inch in (Hameter to as much as 

 a foot or more in length and several inches across. On healthy, vigorous 

 trees they are small and more or less circular 

 in outline. They form funnel-shaped wounds 

 with the small end toward the wood. These I 

 have designated as " pit cankers" (Fig. 58). 

 Often the dead bark remains as a sort of lid 

 to the pit ( Fig. 56) , but it is easily removed 

 with the finger or a knife blade. I have seen 

 young trees with limbs and body literally cov- 

 ered with these pit cankers in all stages of 



Fig. 55.— Canfecr spreading the second season, 

 destroying callus of last season and enlarging 

 area of cankered surface. 



Fig. 54. — Cankers in body 

 of tree resulting from the 

 renewal of activity season 

 after season. Observe 

 that these Started from 

 small pit cankers which 

 partially healed each 

 season. The disease the 

 following season de- 

 stroyed all the bark 

 groii'ih, leaving only the 

 little bit of wood formed 

 in the callus. This still 

 persists. 



healing over. Aside from affording an entrance to rot fungi such cankers, 

 unless they enlarge, do not seriously affect the health of the tree. In many 

 cases these pit cankers do not heal properly or at all, and the disease, 

 spreading the same or the following season, forms the large and dangerous 

 "limb" or "body cankers" (Fig. 59). 



