ISO 



In 1911 Burrill reported its occurrence in Champaign and Montgomery 

 counties, and in 1918 various persons made collections of it in Boone, 

 Cook, Lake, Williamson, Henry, Winnebago, Macoupin, and Bureau 

 counties. E. F. Cuba made an additional collection in DuPage county in 

 1919. At present stem-rvist is known to be present on wheat in 68 of our 

 103 counties, as shown on Map 3. These 68 counties are so distributed 

 as to represent all parts of the state. 



Seasonal variation in the prevalence of stem rust, like that of leaf 

 rust, depends upon the number of infected wheat plants and the amount 

 of infection on each plant. The variation in crop loss is, however, slight, 

 seldom amounting to more than 1 per cent. Stem rust appears later in 

 the season than leaf rust, and the early maturity of our winter wheats 

 not only greatly curtails the period through which injury to the crop may 

 occur, but necessitates proportionately greater degrees of infection for 

 every degree of estimated loss. This fact is illustrated in Table 6. The 

 effect of the joint occurrence of relatively large amounts of diseased leaf- 

 tissue and high percentages of infected stalks became apparent in 1923, 

 when the estimated loss reached 1.5 per cent. 



Our observations, summarized in Table 7, show definite differences 

 in susceptibility to rust infection among wheat varieties. In general the 

 soft winter-wheats which are grown in the southern part of the state are 

 more susceptible than the semi-hard wheats of the Crimean type grown 

 farther north. This is noticeable not only in many fields over wide areas, 

 but also in adjacent fields. 



Control of stem rust in Illinois is difficult. The extreme length of 

 the state from north to south, together with its pecu'iar latitudinal situa- 

 tion, presents many diversities of condition including variations in soil, 

 temperature, moisture, and physiography. Correlated with these condi- 

 tions are diverse factors of an epidemiological nature which serve to 

 complicate the problem further. The growing of resistant varieties such 

 as the hard winter wheats, where these are suitable to local conditions, 

 will serve to minimize crop losses from stem-rust attack. The present 

 tendency throughout the state to increase the acreage of the Turkey 

 wheats promises to materially curtail losses from rust. 



In those sections where only the soft wheats appear to be suitable 

 the early maturity of the crop serves in a large measure to prevent verj- 

 serious crop losses. Nevertheless as considerable ditTerence in resistance 

 to rust appears to exist in the more common varieties of soft wheat under 

 field conditions, a judicious selection from those kinds least susceptible to 

 attack is quite worth while when practicable. Field observations during 

 1923, when stem rust was especially abundant, show the different percent- 

 ages of stalks infected for seven varieties of soft wheat, as indicated in 

 Table 8. Red Cross, Indian Swamp, Fultz, and Fulcaster appear less 

 susceptible than Red Wave, Mediterranean, or Red Chart". 



Throughout tiie northern third of Illinois spring wheat is grown to 

 some extent, and it is in this section of the state thai the common barberry 

 (Bcrbcris Z'ulgaris L.) may be expected to play a part in the development 



