SOME COTTON DISEASES 99 



This disease first makes its outward appear- 

 ance in a cotton field by a sudden wilting of 

 the leaves which turn yellow and fall without 

 apparent reason. 



An examination of the roots of a freshly 

 wilted plant that has been attacked by the 

 wilt fungus always shows a blackened condi- 

 tion of the inner wood of the root or stem. 



So far as known cotton and okra are the only 

 plants the cotton wilt fungus lives on as a 

 parasite. 



This disease cannot be controlled by the 

 application of potash as some farmers suppose. 



The wilt fungus lives in the soil and is 

 spread by the plow, by drainage water, by 

 cattle, by manure, and other means of carry- 

 ing the spores from one place to another. No 

 direct proof is available that this disease has 

 been spread by planting seed from infected 

 fields, but many cases have been reported 

 which indicate that the disease may be spread 

 in this way. 



In every field attacked by wilt there will be 

 found a few plants not affected by the disease. 

 By selecting seed from these plants a strain 

 of cotton may be secured practically immune 



