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Each season the wheat crop is affected adversely by the attack oi 



fungous diseases. The effects of the diseases are shown by reduced 

 yields and often by the inferior quaUty of the grain. There are many 

 of these diseases, and the injuries suffered from their combined attack 

 always result in appreciable losses. Estimates of these losses were 

 placed as low as 4.4% or 2,726,000 bushels in 1918, and as high as 22.0% 

 or 18,524,000 bushels in 1919. During an average year it is thought 

 that the reduction in yield for the state as a whole is between 8% 

 and 9%. 



There is much variation from year to year in the severity of one or 

 more of these fungous diseases. Some are serious every year, and most 

 of the others cause important injury some seasons or in restricted locali- 

 ties. Their destructiveness calls for the thoughtful attention of the 

 wheat grower. 



Rusts 



Two rust diseases have been found on wheat in Illinois. The one 

 known as leaf rust is the more prevalent. Stem rust is common but 

 seldom causes the tremendous losses here that it does farther north. 



Leaf Rust 

 Caused by Piicciiiia triticina Eriks. 



Leaf rust is the most common and the most important of the wheat 

 diseases occurring in Illinois. Even in years unfavorable to its develop- 

 ment it is so abundant that nearly every plant in every field has become 

 infected by the time the grain is mature. Its effect upon the crop is 

 manifested by weakening of the stalks and sometimes by badly shrunken 

 or "shriveled" grain. In extreme cases the weakening of the stalks re- 

 sults in a falling and lodging of the straw, which increases the destructive- 

 ness of the disease by making it difficult or impossible to harvest the 

 crop. 



The disease appears as small reddish spots mostly upon the leaves 

 but occasionally upon the stems. These spots, which lie beneath the 

 epidermis of the leaf and between the veins, are rarely more than one 

 sixteenth of an inch long, but several together may be much longer. The 

 breaking of the epidermis reveals a mass of orange powder within the 

 spot. The grains of powder are the spores of the fungus, and each 

 grain, or spore, is capable under proper conditions of starting a new 

 infection. 



In Illinois, infection takes place cither in the fall or spring. The 

 great acreage of winter wheat gives this rust an opportunity to develop 

 serious infections during the fall on young wheat, and these infections 

 live over the winter, producing spores the following spring and thus 

 continuing the sjiread of the disease until the grain matures. Following 

 the maturity of the grain, the rust develops a "resting stage" which is 



