90 THE CHERRIES OF NEW YORK 



cerasella Aderhold ' and Cercospora circumscissa ^ Saccardo. The ravages of 

 these fungi are prevented by the proper use of bordeaux mixture and lime 

 and sulphur, remedies which, however, must be used with some care to 

 avoid spray injury. With these, as with other fungi, cultivation has 

 a salutary effect as it destroys diseased leaves which harbor the fungi 

 during their resting period. 



Cherry leaves are often covered with a grayish powder which in 

 severe cases causes them to cvirl and crinkle and sometimes to drop. This 

 powdery substance consists of the spore-bearing organs of a mildew ^ 

 (Podosphcera oxyacanthcs De Bary). Powdery mildew is much more 

 common on nursery stock than on fruiting trees and in New York is a 

 serious pest on young cherry trees. In the nursery, injury may be pre- 

 vented by the use of copper sprays or lime and sulphur, either of which 

 is also an efficient preventive in the orchard but the mildew is seldom 

 prevalent enough on orchard plants to require treatment. 



Wherever cherries are grown in either the nursery or orchard, crown 

 gall* {Bacterium tumefaciens Smith and Townsend) has obtained a footing. 

 In the North at least, it seldom greatly injiires old trees, but if the galls 

 girdle a nursery plant serious injury resvilts. Therefore, badly infected 

 young trees showing galls should not be planted. However, but little 

 harm is liable to result under most conditions. When infected plants 

 have been planted it has been found that galls vary greatly in dioration, 

 sometimes disappearing within a year or two and at other times persisting 

 indefinitely. The tumor-like structures are usually at the collar of the 

 plant and vary from the size of a pea to that of a man's fist, forming at 

 matvirity rough, knotty, dark-colored masses. Neither prevention nor 

 cure has been discovered, though it is known that soils may be inoculated 

 with the disease from infected stock and that, therefore, diseased trees 

 should not be planted in soils virgin to the galls. It is probable that there 

 are differences in the susceptibility of Sweet and Sour cherries to the 

 fungus and that the varieties of the two species vary in their resistance 



' Aderhold, R. Mycosphaerella cerasella n. spec., die Perithecienform von Cercospora cerasella Sacc. 

 und ihre Entwicklung, Ber. d. deut. hot. Ges. 18:246-249. 1900. 



' Duggar, B. M. Fungous Diseases of Plants 314. 1909. Pierce, N. B. A Disease of Almond Trees, 

 Jour. Myc. 7:66-67, Pis. 11-14. 1892. 



' Duggar, B. M. Fungous Diseases of Plants 226. 1909. 



* Smith, E. F. and Townsend, C. O. A Plant Tumor of Bacterial Origin, Science 23:671-673. 1907. 

 Tourney, J. W. Cause and Nature of Crown Gall, Ariz. Sta. Bui. 33: 1-64, figs. 1-31. 1900. Hedgcock, 

 G. C. Crown Gall, etc., U. S. Dept. Agr. Bur. PI. Ind. Bui. 90:15-17, Pis. 3-5. 1906. 



