]92 



Ruakura. Further control may be secured by the removal of cultivated 

 or wild buckthorn shrubs in the neighborhood of oat fields. 



Stem Rust 

 Caused by Puccinia gratiiinis Pers. 



The stem rust disease of oats is similar in appearance to stem rust 

 of wheat, and the two diseases are caused by the same fungus. On oats 

 in Illinois stem rust appears much less commonly than crown rust and 

 is not often severe in its attack. 



The earliest record of this disease in Illinois is a collection by A. B. 

 Seymour from McLean county in July, 1881. Further collections were 

 made by him the same year in- Champaign, Fulton, ^IcHenry, and Piatt 

 counties. No further collections or records appear to have been made 

 until 1922, but in that and the following year a distribution of stem rust 

 was found as shown on Map 15. Probably it is much more wide-spread. 



Oat losses from stem-rust attack are rarely severe. Estimates made 

 since 1919 attribute to this disease only a trace of loss annually. An 

 examination in 1923 of 22 fields distributed among 15 counties and in- 

 cluding 705 acres indicated that 16.31 per cent of the stalks were in- 

 fected and that the average amount of diseased tissue on infected stalks 

 was 27.97 per cent. The amount of disease per stalk for all plants, on 

 this basis, would be 4.56 per cent — an amount so small as to have practi- 

 cally no effect upon the expected yield. 



Control of stem rust of oats may be secured in the same manner 

 as on wheat. (See p. 180.) The oat varieties which show resistance to 

 stem-rust infection are few and include especially White Russian, Green 

 Russian, and Ruakura. 



Loose Smut 



Caused by Ustilago areuac (Pers.) Jens. 



Loose smut of oats is similar in appearance to that of wheat already 

 described. The heads are attacked, and the grains transformed to masses 

 of black powder. Losses from this disease are large, and its importance 

 is great. Estimates of crop reduction due to this disease, shown in Table 

 24, for the years 1917-1923 inclusive range from 5 per cent to 7 per cent — 

 equivalent to 5,790,000 to 18,395,000 bushels, with values ranging from 

 two to eleven million dollars. 



The earliest record of this disease in Illinois is a specimen collected 

 by A. B. Seymour at Normal, McLean county, June 26, 1879. In the 

 following years Seymour made collections in Adams. Lake, and McLean 

 counties, thus demonstrating a rather wide occurrence of loose smut fn 

 northern Illinois. In 1900 A. D. Shamel sent out from the Illinois Agri- 

 cultural Ex])criment Station an inquiry concerning the occurrence -of oat 

 snuit in the state. In summarizing the returns, he stated that snuit oc- 

 curred in 12 counties, for the most part widely distributed over the state, 



