APPLE DISEASES 23 



Cause. 



This is a bacterial disease. It is caused by Bacillus amylo- 

 vorus which also attacks the pear, quince, plum, apricot and 

 other trees. The life-history of the parasite on apple may be 

 understood by reading the account under Pear (page 327). 



Control. 



For trees which are less than half girdled, surgical treatment 

 is profitable. Otherwise, bridge-grafting can be followed as a 

 matter of recourse. A draw-shave, mallet, chisel and farrier's 

 knife are desirable tools for the surgery work. Remove the 

 soil from the affected crown and roots. Cut out all discolored 

 tissue, pointing the upper and lower ends of the wound. Wash 

 the cut surface with corrosive sublimate, and after the wound is 

 dry apply a wound-dressing, preferably coal-tar. 



For a full discussion of this disease see Pear (page 323) . 



REFERENCES 



Whetzel, H. H. The blight canker of apple-trees. Cornell Univ. Agr. 



Exp. Sta. Bui. 236 : 103-138. 1906. 

 Orton, C. R., and Adams, J. F. Collar-blight and related forms of 



fire-blight. Pennsylvania Agr. Exp. Sta. Bui. 136 : 3-23. 1915. 

 Hewitt, J. L. Twig blight and blossom blight of the apple. Arkansas 



Agr. Exp. Sta. Bui. 113 : 493-505. 1913. 

 Whetzel, H. H. Fire blight and apple-tree canker. Wisconsin Hort. 



Soc. Ann. rept. 36 : 215-226. 1906. 

 Swingle, D. B. The pear and apple blight in Montana. Montana 



Agr. Exp. Sta. Circ. 2 : 1-9. 1910. (Revised : pp. 1-14. 1911.) 



STIFFEN, OR BITTER-PIT 

 Caused by fluctuating water supply 



It is difficult to estimate the importance of this disease. 

 Apples are not destroyed, but their appearance and quality 

 are affected in a manner not easily measured. Figures repre- 

 senting reliable investigation into the amount of losses are not 



