ENEMIES AND ^DISEASES OF CORN 271 



ones of importance are corn-smut (Ustilago zea) and 

 different kinds of ear-rots. 



327. Corn-smut -(Fig. 45) often causes enormous en- 

 largements on the ear, tassel, or stem of the corn plant. 

 The infection usually does 

 not occur until the plaflts 

 are a foot or more high. 

 The spores of the disease 

 are carried over in the 

 soil so that when land 

 becomes infected with 

 corn-smut it is likely to 

 injure the crop each year 

 unless some crop other 

 than corn be grown, or 

 unless precautions are 

 taken to cut out and burn 

 all infected plants before 

 the smut-balls reach that 

 stage of development at 

 which the skin breaks and 

 sets free the spores. The disease may also be carried from 

 year to year in manure which has been made from feed- 

 ing the diseased plants. No treatment of the seed is 

 effective. 



Fig. 45. — Corn-smut. 



