VII 



SWEET POTATO 



237 



SWEET POTATO 



The sweet potatoes are grown extensively in both 

 tropical and temperate zones. The diseases occurring 

 in the United States have been the subject of extensive 

 studies, but our information concerning the diseases 



FIG. 83. Sweet potato affected with black rot, Sphaeronema fimbriatum. 

 (Photo by J. J. Taubenhaus.) 



occurring in the tropics is decidedly meagre. Very 

 little can be given at this time except a discussion of 

 those diseases which probably occur in the tropics, 

 especially the American tropics. 



Black Rot. This disease is due to Sphaeronaema 

 fimbriatum, (Ell. & Hal.) Sacc. (Fig. 83), and occurs in 

 the seed bed, causing a discoloration on roots and stems 

 of the seedlings which is known as black shank. On 



