MANUAL OF FRUIT DISEASES 



the diseased portion is sunken. 

 Older spots become lobed, due to the 

 secondary extension of the pathogene 

 from one or more points in the leaf. 

 This activity results in a series of 

 more or less concentric areas mak- 

 ing up an irregular spot, but in which 

 the outline of the original diseased 

 portion can still be recognized (Fig. 

 12). The center of the lesion be- 

 comes grayish brown and the entire 

 affected area presents an appear- 

 ance which has given rise to the name 

 frog-eye (Fig. 12). Frequently the 

 small black fruiting bodies of the 

 pathogene develop on the leaf-spot, 

 although they are not always readily 

 noticed on account of their minute- 

 ness. The spots are not so conspic- 

 uous on the lower surface of the 

 baf. In severe cases the foliage 

 turns yellow and may fall six or 

 eight weeks prematurely. Bor- 

 deaux injury is very similar to this 

 leaf-spot. 



The cankers (Fig. 13) are found 

 more often on the uppermost side of 

 the larger limbs. At first the bark 

 is discolored and sunken. The dis- 

 coloration is for a short time red- 

 dish brown but very soon is darker, the diseased portion, upon 

 close examination, being easily distinguished from the surround- 

 ing healthy bark. Sometimes the cankers remain small and the 

 pathogene dies at the end of the year. In other lesions the 



FIG. 13. Black-rot canker. 



