177 



to be found chiefly upon the under side of the leaves and on the stalks, 

 where it appears as covered spots, similar in size and shape to the others 

 but black. 



The period between harvest and the appearance of the new crop 

 is bridged' by infections on volunteer wheat in clover and other second- 

 ary crops. There is an alternate stage, ^ similar to that ascribed to stem 

 rust, which occurs on 12 species of meadow rue (Thalictrum), but it is 

 noteworthy that in Illinois our common meadow rue (T. dioicum L.) 

 has not been found rusted. 



The history of the introduction and spread of leaf rust in Illinois 

 is not known. The first definite record of its occurrence in this state 

 is a specimen collected by A. B. Seymour in McHenry covmty August 

 22, 1881. The following year specimens were collected in Adams county 

 June 2G, 29, and July G, and in McLean county July 17. In 1883 C. A. 

 Hart collected leaf rust in Adams county, and during later years G. P. 

 Clinton made several collections in Champaign, Ogle, and Knox counties. 

 H. W. Anderson has collected specimens in Pike county, and H. L. 

 Bolley^ has recorded its presence in eastern Illinois in 11)05. 



Field observations of the past three seasons have brought together 

 a large quantity of additional data on the distribution of the disease 

 throughout the state. In 1922, specimens were collected in 140 places 

 distributed widely over the state and showing the occurrence of leaf 

 rust in 83 of the 102 counties. Those counties from which specimens 

 were not secured are widely dispersed, and are so distributed that col- 

 lections made in adjacent counties indicate the occurrence of leaf rust 

 in them as well. 



During 1923 additional collections of rust were made, resulting in 

 a large compilation of field notes. From these the distribution of leaf 

 rust is seen to include practically the entire state, as shown on Map 2. 

 Indeed, from our observations it appears highly improbable that in the 

 whole state there occurs a single field of wheat in which at least some 

 leaf rust can not be found. 



Losses from this disease are difficult to determine, but for the years 

 1919-1923 inclusive they have been estimated to vary from 0.5 per cent 

 (221,000 bushels) in 1920 to 10 per cent (5,543,000 bushels) in 1922 

 (see Table 1). The annual losses can not be apportioned among the 

 counties nor according to any lateral or longitudinal division of the state. 

 There is to be seen, however, a marked correlation of abundance and 

 severity of infection with the growing of soft winter-wheats such as 

 Red Wave, Early May, Fultz, Blue Stem, Harvest Queen, and Fulcaster. 



The variation of leaf-rust infection from season to season depends, 

 as is indicated in Table 2, upon both the number of infected stalks and 



' Valleau. W. D., Over-sumiTiering of leaf ru.st of cereals in Kentuck.v. Phyto- 

 path. 13: 338-340, 1»23. 



'.laekson. H. S., and Mains, E. B., Phytopath, 11: 40, 19»1 : also Jour. Akf. Res. 

 22: l.';i-172, 1921. 



•Scl., n. 8., 22. 51. 1905. 



