374 MAINE AGRICULTURAL EXPERIMENT STATION. I9IO. 



branches is very characteristic and they can be recognized by 

 one who has become somewhat famihar with the various can- 

 kers and twig bHghts, without microscopic examination of the 

 fungus. There is some reason to beheve that the fungus is not 

 a very active parasite and it may be possible that such diseased 

 branches have been injuriously affected by some other agency 

 before the attack of this fungus.* 



Coryneum and Phoma cankers. In the examination of apple 

 cankers the. spores of Coryneum foliicolum and Phoma mali have 

 been found of quite frequent occurrence. Inoculation experi- 

 ments in 1909 proved that both of these fungi were capable of 

 causing disease of healthy bark of apple branches. For a de- 

 tailed account of the study of these fungi the reader is referred 

 to Bulletin 170 of this Station. The appearance of different 

 stages of Coryneum cankers is shown in Figs. 262 and 263. 



Cytospora canker. A species of Cytospora has frequently 

 been found on small branches which have been killed back but 

 no true cankers have been seen. Those lesions observed have 

 much the same appearance as has been described for branches 

 on which Myxosporium is found. After a little experience one 

 can distinguish the two fungi on the bark without the aid of the 

 microscope. 



In Bulletin 191 of the New York Station it is suggested that 

 a species of Cytospora found on diseased apple branches in that 

 State is probably parasitic. The Cytospora which occurs on 

 apple branches in Maine has been isolated, grown in pure cul- 

 ture where it fruits abundantly, and inoculations have been made 

 in small branches in the orchard. The fungus made only a 

 slight development in the injured tissue at the points of inocu- 

 lation, while inoculations made the same day on the same 

 branches with Sphacropsis developed well r*arked cankers. The 

 indications are that the species of Cytospora which is found in 

 Maine is very slightly if at all parasitic. 



Pear blight canker. The canker of apple trees caused by the 

 pear blight organism. Bacillus aniylovorus (Burril) DeToni., 



* The fungus has been isolated from such diseased branches and has 

 been grown in this laboratory upon sterilized apple wood and bean pods 

 for several months. Spores were produced in the cultures about one 

 month after the fungus was transferred from plates to bean pod 

 tubes. Some inoculations have been made and the results of these 

 will be given in a later publication. 



