European Apple Canker (Nectria ditissima Tul.). 

 This canker (ITig. 4) is usually characterized by ugly 

 scars, due to the distortion of the tissue by the fungus named 

 above. It is less common than the preceding canker, except 

 on neglected trees, where it sometimes does much injury. 

 Our earliest New England literature refers to canker on 

 apple trees, and it is not unlikely that this is the one meant. 

 In most cases it seems to follow injuries from various causes. 

 Where the disease is severe it should be pruned out. 



Nectria Canher (Nectria cinnaharina (Tode) Fr.). 

 This fungus (Fig. 5) is responsible for a canker which 

 is characterized by the production of numerous cinnamon- 

 colored pustules on the bark of dead wood. It is occasion- 

 ally seen on apple trees, but more commonly on winterkilled 

 branches of maples, horse chestnuts, etc. So far as our 

 observations go, this is invariably a dead wood fungus fol- 

 lowing injuries of different types. The fungus penetrates 

 the bark and wood and gives rise to discolored areas of the 

 woody tissue. 



Blight Canker. 

 A canker of rare occurrence with us has been described by 

 Dr. H. H. Whetzel (Fig. 6). It is caused by the apple and 

 pear blight organism, and occurs most frequently on young, 

 smooth bark trees and on water sprouts. The diseased areas 

 are smooth, sunken and brown in color, and there is no 

 formation of pustules. The freshly affected tissues are 

 usually watery, and in older cases cracking of the bark 

 occurs. More often infection is confined to the bark, causine; 

 no injury to the wood. It is believed that only a small per- 

 centage of this canker lives through the winter to serve as a 

 source of infection the following year, and that insects play 

 some part in the work of infection. Another source of in- 

 fection is the pruning knife. 



