152 MANUAL OF FRUIT DISEASES 



on Oldenburg apples while still hanging on the tree at Ithaca, 

 New York, by the junior author. Later it was found in market 

 fruit. So far, it has done no great damage in the United States, 

 partly due, no doubt, to its very limited range. Up to date it 

 has not been reported outside of New York State, although it 

 ... ,^ ^ ^ doubtless occurs, to some extent 



a ^ l eas t> m several of the apple 

 regions of North America. 



The disease is induced by the 

 fungus Phytophthora cactorum. 

 Affected apples w r ere first ob- 

 served in July on those fruits 

 nearest the ground. Earlier 

 infections were not seen. These 

 facts indicate strongly that the 

 source of the inoculum is the 

 soil. Infections occur up to the 



FIG. 40. Phytophthora-rot of apple. . . . PIP- 



time or the ripening 01 the fruit. 



A brown-rot is produced which in many respects closely re- 

 sembles fire-blight lesions on apple fruits (Fig. 40). The 

 affected portion appears water-soaked at first, the margin is not 

 definite, and there are no external evidences of fungus fruiting 

 bodies. 



REFERENCES 



Whetzel, H. H., and Rosenbaum, J. The Phytophthora rot of apples. 



Phytopath. 6 : 89-90. 1916. 

 Osterwalder, A. Die Phytophthorafaule beim Kernobst. Centralbl. 



f. Bakt. 2:15: 435-440. 1905. 

 Bubak, Fr. Die Phytophthorafaule der Birnen in Bohmen. Zeitschr. 



f. Pflanzenkr. 20 : 257-261. 1910. 



