Minnesota Plant Diseases. 



299 



stroyed and only the loose strings of the woody tissues of the 

 head branches remain. The head smut can be distinguished 

 from the grain-smut by this habit. The smut mass forms a 

 blackish powder. 



No preventives are known for this smut. It is possible that 



the treatment for grain 

 smut will be effective. 



Grain smut of sorghum 

 [Sphacelotheca sorghi (Lk.) 

 C lint n]. This sorghum 

 smut attacks the young 

 grains and forms smut 

 masses in them, but does 

 not destroy the glumes. 

 The smutted grains increase 

 in size, chiefly in length, 

 and have a whitish wall 

 which encloses a mass com- 

 posed entirely of spores. 

 The spores rest over winter 

 and under proper condi- 

 tions, in the spring time, 

 form more spores, which 

 can in turn multiply in 

 yeast-like fashion ; the re- 

 sulting spores are capable 

 of causing infection. 



Sorghum is also fre- 

 quently attacked by other 

 smuts and certain varieties 

 of the sorghum are known 

 to be peculiarly susceptible 

 to smut. (See also Head 

 Smut of Sorghum.) 



A few experiments on 

 this smut have indicated 

 that hot water treatment 

 may be beneficial. It has proved successful in the treatment of 

 the same smut on broom corn. It is also possible that the for- 

 malin method would be effective and useful. 



Fig. 149. — Corn smut (Ustilago maydis), on an 

 ear of corn. A few of the kernels near the 

 butt have not been smutted. All of the 

 others have been attacked and have in- 

 creased enormously in size. The enlarged 

 kernels are filled with the smut powder. 

 Original. 



