CHAPTER XIX 

 CEREAL PESTS PARASITIC FUNGI 



NORTH AMERICAN farmers, without doubt, suffer an aver- 

 age loss of at least 50 million dollars annually from fun- 

 gous diseases of small grains. Except for the rather com- 

 mon practice of seed treatment for prevention of smut, in 

 recent years, the loss would be much greater. 



The cereal diseases are included approximately in three 

 main groups : (1) rust diseases, (2) smut diseases, and 

 (3) miscellaneous diseases, or those caused usually by 

 imperfect fun^i. 



CEREAL RUST DISEASES 



Among the oldest known of all cereal diseases, and yet 

 probably the least understood, are those caused by rust 

 fungi. They are, moreover, exceedingly destructive. 

 In 1904 it was estimated that the loss from these rusts 

 to the three states of Minnesota, North Dakota, and 

 South Dakota, alone, was fully 25 million dollars. Severe 

 losses occurred in these same states again in 1914. 



550. The orange leaf -rust (Pucdnia rubigo-vera, DC.). 

 This is the most generally distributed of all cereal 

 rusts, and is the earliest rust to appear in the spring. In 

 this country it occurs on wheat, rye, and several other 

 grasses. It is so named from the color of the uredosori, 

 which occur chiefly on the leaves. Over twenty years ago 



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