DISEASES 155 



It will be observed that wheat and all the mill by-products 

 are richer in protein than corn, while corn is richer in carbo- 

 hydrates than any of the wheat products. 



DISEASES AND INSECT ENEMIES 



196. Diseases. It is very seldom that a crop of wheat 

 is matured without being affected to some extent by some of 

 the common diseases to which the crop is subject, as scab, 

 rust, and smut. There are other diseases, but so little is 

 known about them that only the three named will be dis- 

 cussed here. Disease causes an immense loss to wheat and 

 other cereal crops every year, whereas considerable might be 

 done to check this loss. 



(a). Scab. Scab is a fungous disease which attacks the 

 glumes, or chaff, of the wheat plant. It is not very common, 

 but sometimes causes much loss, for shrunken kernels result 

 when the wheat plants are affected. Usually only a few 

 glumes are affected, and these are identified by pinkish spots 

 at the base. There is no known treatment for this disease, 

 except that the stubble be burned, if wheat is to follow a 

 crop of wheat affected with scab. 



(^). Rust. Rust occasionally causes immense damage 

 to the wheat crop, sometimes ruining the entire crop of a 

 great part of the country. It is a fungous disease which is 

 almost always present to some extent, and which, when 

 conditions are favorable, may spread rapidly and cause the 

 straw to become very weak, resulting in shrunken kernels. 

 There are two kinds, the leaf rust and the stem rust. The 

 former is nearly always present, but the latter is by far the 

 more destructive. Stem rust may hve over winter on the 

 ripened plant, or more commonly in another form on some 

 other plant. The spores may germinate and attack the 

 wheat at any stage during its growth. No remedy is known 

 except the selection of varieties of wheat which are rust 

 resistant, though attempts in this direction have not as yet 



