8 THE RUSTS OF GRAINS IN THE UNITED STATES. 



An average reduction in yield of 1.75 bushels per acre in 1904 

 as compared with the preceding and following years gives a total 

 reduction of over 23,000,000 bushels, valued at more than $15,000,000.1 

 The greater part of this reduction in yield and consequent loss 

 was undoubtedly due to rust. It is exceedingly conservative to 

 put the loss in these three States in 1904 as high as $10,000,000; 

 and when we consider the additional losses in the other wheat-growing 

 districts of the United States the aggregate is enormous. 



KINDS OF RUSTS IN THE UNITED STATES. 



This paper deals only with the rusts of the small-grain crops, 

 wheat, barley, rye, and oats, and includes the following forms :^ 



Puccinia graminis Pers. on wheat, rye, oats, and barley, commonly known by the 

 misleading term "black rust," but more appropriately known as "stem rust," 

 as it generally is confined more or less closely to the stem and sheath (PI. I). 

 P. rubigo-vera tritid^ on wheat, known as "orange leaf rust, "or "leaf rust of 



wheat." 

 P. rubigo-vera secalis^ on rye, known as "orange leaf rust," or "leaf rust of rye." 

 P. coronuta Corda. on oats, known as "leaf or crown rust of oats." 

 P. simplex (Korn.) Erikss. and Henn. on barley, known as "leaf rust of barley." 



These rusts, in common parlance, are classed as stem or leaf rusts, 

 a convenient grouping which directs attention to the chief though 

 not exclusive location of the rust on the host plant. 



DISTRIBUTION OF RUSTS IN THE UNITED STATES. 

 GENERAL STATEMENT. 



All of the grain rusts, with the possible exception of stem rust of 

 rye and the leaf rust of barley, are found throughout the United 

 States wherever their host cereals are grown. As to the distributon 

 of the barley leaf rust, less is known, because it may have been but 

 recently introduced into tliis country and appears, as a rule, late in the 

 season. It has been reported from Cahfornia, Virginia, IVIinnesota, 

 and Iowa and is probably of wide distribution. 



Although the rusts are for the most part practically coextensive 

 with the hosts, they are not serious in all locahties. Epidemics may 

 occur in almost any grain-growing region, but they occur less fre- 

 quently in some sections than in others. In general, the area most 

 affected is the valley of the Mississippi and its tributaries, compris- 

 ing the region west of the Alleghanies and east of the ninety-eighth 



1 Even comparing the yield, 11. Co bushels per acre, with the 10-year average (12.2 bushels per acre) for 

 the three States from 1890 to 1905 (obtained by computing the averages in the three States), tliere was a 

 reduction in yield in 1904 of more than 0.5 bushel to the acre. 



2 A few other rusts have Ijeen reported, some perhaps by mistake and some of such rare occurrence as to be 

 of no economic importance. Puccinia glumaruw (Schm.) Erikss. and llenn., the yellow rust of wheat, 

 which is a vt^y common ami serious rust in Europe and India, has not yet appeared in this country. 



' The trinomial terminology for these two rusts was lirBl used by Carleton (30, p. 10). 



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