APPLE DISEASES 



457 



are mature, pinkish masses of spores 

 exude. The spores from canlvers cause 

 much of the early infection of fruit on 

 the tree each year. 



Myxosporiiini Canker 

 The fungus causing this disease has 

 been much confused in the past with 

 Spliaeropsis maJorum. The two are en- 

 tirely distinct. So far as observed the 

 damage which it does is confined to kill- 

 ing outer portions of the hark on old 

 limbs and the killing back of the bark 

 on younger limbs and twigs rather than 

 to the production of true cankers. On 

 such branches the fruiting pustules are 

 found on the part which was first killed. 

 The dead bark is separated from the 

 healthy bark by a sharp line and is 

 sunken. The appearance of these branches 

 is very characteristic and they can be 

 recognized by one who has become some- 

 what familiar with the various cankers 

 and twig blights, without microscopic 

 examination of the fungus. There is 

 some reason to believe 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. 



Corynenni and Plioma 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 have proved that both of these 

 fungi were capable of causing disease of 

 healthy bark of apple branches. For a 

 detailed account of the study of these 

 fungi the reader is referred to Bulletin 

 170 of the Maine Station. 



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 appear- 

 ance 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. 



Pear Blight Canker 



The canker of apple trees caused by 

 the pear blight organism. Bacillus amyl- 

 ovonis (Burril) DeToni., has been re- 

 ported as causing a great amount of 

 damage in apple orchards in various 

 states. 



See Pear Blight under Pear. 



W. J. MOBSE, 



Orono, Maine. 

 Club Tip. See Rosette. 



Collar Bliarht 



A form of pear blight attacking the 

 apple at the thickened portion of the 

 tree just above and below the ground 

 line. 



See Pear Blight under Pear. 



Some forms of collar disease are the 

 result of winter injuries followed by the 

 entrance of fungus disease. 



Collar Rot Phase. See Blight under 

 Pear. 



Core Decay of Baldwin 



A core decay of stored apples was in- 

 vestigated by H. J. Eustace, of the New 

 York Experiment Station, in 1903. This 

 decay occurred quite generally in Bald- 

 wins but was not confined to that va- 

 riety. 



The apple shows decayed tissue about 

 the core, which is brown, dry-rotten and 

 tasteless, but surrounded by healthy 

 tissue. 



The trouble was not traced to any 

 fungus or bacterium. It appeared under 

 a variety of soil conditions. The Bald- 

 wins that year overbore and storage 

 conditions may have been responsible 

 for a part of the trouble, as only com- 

 mon storage apples seemed to be affected. 



Crown Gall 



Bacterium tumefaciens 

 H. P. Barss 

 Crown gall is a very common and 

 widespread disease known under a vari- 

 ety of other names such as "galls." 

 "tumors," "root knot." "crown knot," 

 "woolly knot," "hairy root," etc. It has 

 been reported from every state in the 

 Union and from Canada. Europe, Africa 

 and Australia as well. It attacks the 

 apple, prune, peach, cherry, raspberry 



