338 FIELD CROPS FOB THE COTTON-BELT 



for these rusts. They can be controlled to a large extent 

 by growing rust-resistant varieties. For a description 

 of rust see the chapter on Fungous Diseases of Oats,' 

 p. 301. 



The two common smuts of wheat are the loose smut 

 (Ustilago tritid) and the covered smut (Tilletia fee tens). 

 The latter disease is often called bunt or stinking smut. 

 Both of these diseases are preventable. 



416. Loose smut. — This disease turns the entire 

 wheat head, including the chaff, into a black powdery mass 

 which is usually blown away by the wind, leaving only 

 the bare rachis with a few smut spores sticking to it. The 

 seed treatment for this disease is rather difficult on account 

 of the fact that the smut lives over inside the wheat kernel. 

 The spores, which are ripe at flowering time, find lodgment 

 in the flowers of unaffected wheat plants. These spores 

 soon germinate and send a little filament into the young 

 kernel, which later develops into a young smut plant. 

 This, however, does not interfere with the development of 

 the kernel, and the disease is thus carried over inside the 

 kernel to the succeeding crop, where it again becomes 

 evident at flowering time. 



This disease can be prevented by subjecting the seed to 

 what is known as the modified hot-water treatment, which 

 is as follows : Soak the seed for not less than four hours or 

 more than six hours in cold water. Rernove, drain, and im- 

 mediately immerse the seed for a moment in water kept at 

 a temperature of about 120° F.; the seed is then immersed 

 for 10 minutes in water kept at a constant temperature of 

 129° F. Comparatively small quantities of seed should be 

 treated at a time so that all of the seed may become 

 equally heated. Water heated above 129°F. must not be 

 used. This treatment is most safely used in connection 



