816 PRINCIPLES OF SOIL MICROBIOLOGY 



For the control of potato scab, sulfur is used with success. Care 

 must be exercised, however, in using the proper amounts, so as not to 

 make the soil too acid. Sweet potato scurf and pox of sweet potatoes 

 can also be checked by the application of sulfur. Organisms like 

 Pythium (damping off of seedlings) and Spongospora subterranea are in- 

 tolerant to acid, while the myxomycete Plasm odiophora brassicae 

 (finger and toe disease) is kept in check by addition of lime. 



