324 Diseases of Truck Crops 



from the main thread by a cross wall. The antherid- 

 ium resembles that of P. phaseoli. Mature oospores 

 have a medium , thick, smooth, hyaline wall. It is 

 not known how the oospores germinate. For meth- 

 ods of control, see p. 337. 



PHOMA ROT 

 Caused by Phoma solani Mel., Rosen., and Sch. 



Phoma rot is found only on bruised tubers. It is 

 also found following injuries produced by powdery 

 scab, Spongospora subterranea. The lesions of phoma 

 rot are brownish dark to gray dark sunken pits with 

 irregular and sharply defined margins. The black 

 pycnidia (fig. 61 h) are found scattered over the entire 

 surface of the lesions. The disease may cause con- 

 siderable damage in storage. The remedy consists in 

 careful handling of the tubers during digging and 

 storing. 



ANTHRACNOSE 



Caused by Colletotrichum atramentarium (Berk, 

 and Br.) Taub. 1 



Anthracnose was first described by O'Gara 2 as 

 a disease attacking the foot of the plant. The 

 fungus was originally named Colletotrichum solani- 

 colum O'Gara, but was later changed by the 

 writer to C. atramentarium. It causes deep lesions 



1 Taubenhaus, J. J., Mem. N. Y. Bot. Card., 6 : 549-560, 1916. 



2 O'Gara, P. J., Mycologia, 7 : 38-41, 1915. 



