CEREAL EUSTS OF THE UNITED STATES : A PHYS- 

 lOLOUICAL INVESTIGATION. 



INTRODUCTION. 



The investigator of grain rusts learns three important facts at the 

 beginning of his work : (1) That these rusts are more or less distributed 

 over all parts of the world where cereals are grown, (2) that the average 

 annual losses thej^ cause are very much greater than is generally sup- 

 posed, and (3) that as yet little is known regarding their ontogenetic 

 relations to each other and to their host plants. In view of the impor- 

 tance of rusts from a botanical standpoint, it is rather surprising that so 

 little attention has been given to their study. In only two of tlie princi- 

 pal cereal-growing countries — that is, Australia and the United States — 

 have any investigations of cereal rusts been made, and even in Aus- 

 tralia, through the investigation of rust resistance, the matter has 

 drifted into a study of the wheat plant itself rather than of the rusts 

 that affect it. In the important cereal regions of Eussia, India, and 

 Argentina practically nothing is known about these rusts. 



The only studies of the physiological relationships of the grain rusts 

 outside of the writer's, most of which are reported in this bulletin, are 

 those by Dr. Jakob Eriksson, of Sweden, whose researches will be 

 described further on. Several investigations, relating almost wholly to 

 the application of fungicides and the wintering of the parasite, have 

 been made in this country. The most important are those reported by 

 Bolley (6-10),i Kellerman and Swingle (41), Pammel (54, 5G), Galloway 

 (34), and Hitchcock and Carleton (38, 39). 



A brief review of the work on grain rusts so far carried on shows 

 that three distinct phases of the subject have been investigated: (1) 

 The value of fungicides in preventing or checking rust, (2) rust-resistant 

 varieties, and (3) the physiology of the rusts. Much of the work of 

 the American writers above named pertains to the iirst phase. Besides 

 the experimental work with the common fungicides, special attention 

 was given to the preparation and application of new ones, particularly 

 in the work in charge of the Department (34, Jour. Myc, pp. 199-203). 

 In these trials the seed and soil were also treated with various com- 

 pounds. The results of these various experiments showed that although 



' For explanation of this and similar references in this bulletin, see corresponding 

 numbers in bibliography, pp. 70-73. 



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