191 



western parts of the state, while in the northern and eastern parts large 

 acreages occur. If a line be drawn approximately from Rock Island 

 through Havana to Mattoon and eastward, it will be found that nearly 

 85 per cent of the states oat acreage lies north of the line, with especial 

 concentration in Lee and Ogle counties to the north, and Iroquois, Cham- 

 paign, and McLean counties to the east. 



Crown Rust 

 Caused by Puccinia coronata Cda. 



Crown rust of oats is similar in many ways to stem rust of wheat, 

 and one may easily be mistaken for the other since both attack oats. 

 As a rule, however, the black stripes of the crown rust do not appear 

 broken and ruptured as do those of stem rust, but remain covered by 

 the epidermis of the plant. 



This disease was first reported in Illinois in Adams county in 1881 

 by A. B. Seymour. It has since been found by Seymour, Anderson, and 

 others in McLean, Tazewell, McHenry, and Lake counties. Its distribu- 

 tion as now known is shown on Map 14. It is prevalent in all parts of 

 the state. 



It has been estimated that during the year 1910-1923 inclusive, crown 

 rust caused a reduction in the oat crop varying from 1 per cent in 1919 

 to 4 per cent in 1923. As indicated in Table 22, these reductions ranged 

 from 1,323,000 to 4,583,000 bushels and in valuation from $782,000 to 

 $1,787,000. 



In 1922 an examination of 42 fields of oats, distributed among 23 

 counties and including 538 acres, indicated an average crown-rust in- 

 fection involving 91,038 per cent of the stalks and an average amount of 

 diseased tissue per stalk of 58.05 per cent. In 1923 a similar examina- 

 tion, covering G9 fields distributed among 26 counties and including 122(J 

 acres, showed a crown-rust infection involving 90.85 per cent of the 

 stalks and an average amount of diseased tissue per .stalk of 36.94 per 

 cent. These differences between two years are shown in Table 23 in 

 connection with estimated percentages of crop reduction, and from this 

 comparison it appears that the annual variation in crop-injury is, as in 

 the case of the wheat rusts, not so much a matter of the number of 

 diseased plants, as of the amount of diseased tissue on each plant. 



Crown rust has an alternate stage on the buckthorn {Rhaumm 

 catharlica L.) similar to that described for stem rust of wheat. In north- 

 ern Illinois, where this shrub is commonly used for hedges, it has been 

 responsible for local epidemics of considerable ini])ortance. 



Control measures involve the use of resistant varieties,' among which 

 are Appier, Burt, Early Ripe, Golden Rustproof, (ireen Russian, and 



• DurroH. L. W,. an<l ParU.r. .1. H. "romp.-iratlve Resistance of Varieties of Oats 

 to Crown and Stem Rusts," Iowa Acrlcultural Experlnunt Station Research Bulletin 

 62. 1920. 



