10 THE RUSTS OF GRAINS IN THE UNITED STATES. 



it is always present and almost always virulent. Little grain is grown 

 in this region. In the Southern States only a small quantity of 

 wheat is grown, and here this rust is often severe. In the south- 

 ern half of Texas it makes wheat growing a hazardous undertaking. 

 Even in northern Texas it is a factor of great importance. The 

 greatest rust epidemic of the last decade, which was due to the stem 

 rust of wheat, occurred in 1904 and extended over the entire Missis- 

 sippi Valley and up into the wheat fields of the Canadian Northwest, 

 being particularly severe in the spring-wheat belt. It invaded the 

 dry lands west of the Rocky Mountains and was severe in the interior 

 valleys of California. A serious attack of stem rust of wheat was 

 also experienced in the spring- wheat belt in 1902 and in 1905. 



Leaf rust of wheat. — The occurrence of leaf rust (Puccinia rubigo- 

 vera tritici Carleton) is also coextensive with wheat culture. It is more 

 common in many districts than stem rust. In the whole eastern 

 half of the United States it is present every year, usually to a consider- 

 able extent. Visitations amounting to epidemics are not infrequent, 

 but the losses caused are not comparable to those of the stem-rust 

 epidemic and are disregarded by the ordinary farmer, who accepts 

 them as inevitable. In the Atlantic States the leaf rust is the chief 

 rust of wheat and is very severe in some seasons. Like the stem rust, 

 it follows more or less closely the rainfall lines, being of little impor- 

 tance in the arid sections of the country. In the Palouse district of 

 Washington, Idaho, and Oregon, however, it is usually abundant. 



Stem and leaf (or crown) rusts of oats. — The presence of stem and leaf 

 rusts of oats (Puccinia graminis avenae~E,rikss. and Henn., and Puccinia 

 coronata Corda) is coextensive with the culture of that grain. The 

 stem rust of oats, if not more harmful, is fully as destructive as the stem 

 rust of wheat, and its distribution is somewhat similar. It is almost 

 invariably accompanied by the leaf rust (Puccinia coronata), which 

 is probably the most destructive of the leaf -rust group. 



Attention should be called to the fact that the stem rust of oats is 

 not nearly so closely confined to the stem as is that of wheat, but is very 

 frequently found on the leaf blades. The leaf and stem rusts of oats 

 are usually commingled, and it is difficult to determine how much of 

 the resulting damage is due to each. The leaf rust, however, is seldom 

 found on the spikelets or the spikelet stems. It is here that much 

 of the real damage is done by the stem rust. These rusts are found 

 extensively only east of the dry belt of the Great Plains region, with 

 the possible exception of eastern Oregon and Washington. In the 

 Gulf Coast States, except northern Texas, and in Georgia and South 

 Carolina they are paramount in importance and almost prohibitive 

 of spring-oat growing, though winter oats are quite extensively grown. 

 Proceeding northward, the rusts continue to be of great importance. 



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