22 



N. H. AGR. EXPERIMENT STATION. [Bulletin 157 



contagious. Great care 

 should be taken to reject 

 all diseased plants at the 

 timeoftransplanting. The 

 disease usually does the 

 greatest damage on 

 nurserj^ stock. 



EUROPEAN APPLE 

 CANKER. 



Nectria cUtissijiiu Tul. 



This disease is reported 

 as serious in the orchards 

 of Europe, and is appar- 

 ently becoming distribu- 



Fig. 26. — Crown Gall on Apple. 



uted in America. It is not of so 

 common occurrence in New Hamp- 

 shire as the black rot canker, but is 

 more destructive where found. The 

 fungus seems to be dependent upon 

 wounds for entrance to the host 

 tissue. It attacks the inner bark and 

 the cambium, and to some extent 

 the young wood. The mycelium is 

 perennial in the host. As the new 

 growth develops around the wound 

 it is attacked and killed by the fun- 

 gus; thus a series of ridges may be 

 developed, giving a characteristic ap- 

 pearance to the disease (Fig. 27). 

 Two kinds of summer spores are 



Fig. 27. — European Apple Canker. 



