243 



In 1911 leat spot was reported by Burrill in Champaign comity and 

 in a group of 8 counties in southern Illinois; but in 1912 in Champaign 

 county only. 



At present leaf spot is known to occur in 26 counties, the distribu- 

 tion of which is shown on Map 101. It appears to be wide-spread over the 

 state, but in northern Illinois it is only occasional, while in southern Illi- 

 nois it is apparently common. 



Loss from this disease is not usually great, but may at any time 

 become so. Control is readily obtained with Bordeaux mixture. 



Sweet Potato 



According to the 1920 census, there were cS,ii03 acres in Illinois de- 

 voted in 1919 to the raising of sweet potatoes, with a yield of 6(!8,S1.") 

 bushels. According to the reports of the State Agricultural Statistician 

 the acreage since 1919 has been about 9,000 acres, yielding between 

 850,000 and 990,000 bushels, valued at from $890,000 to $1,179,000. 



Only 8 counties are reported to have no commercial acreage in 1922. 

 For the most part the county acreage is small, running from 3 to 90 

 acres. Union county is an outstanding producer, with an acreage of 

 1,974. Johnson and Pulaski counties each has over 500 acres and Will- 

 iamson over 400. The acreage of important counties is indicated on 

 Map 102. The principal sweet potato region lies, therefore, in southern 

 Illinois, with a considerable acreage also in Adams and Cass counties. 



Illinois shares fifteenth rank in acreage with Delaware and Mary- 

 land. In yield per acre it ranked seventh in 1 !)2 1 . and in total ])ro(luc- 

 tion in the same year it ranked sixteenth. 



Two diseases appear to be common in Illinois. 



Black Rot 



Caused by Sphaeronema fiiiibriatmii (II. & H.) Sacc. 



Black rot is the most serious disease of sweet potato in Illinois. 

 Dark brown to black spots appear on the surface of the potato and ex- 

 tend in all directions, finally involving the entire root. In storage the 

 rot is also extremely destructive. 



This disease is known to occur in Illinois in ihe six counties indi 

 cated on Map 103. They are widely distributed over the .state but in- 

 clude only two counties— Pulaski and Cass — with a large sweet potato 

 acreage. 



For a control of this disease the use of disease-free roots in start- 

 ing cuttings, the maintenance of seed beds free from the disease, and 

 the cultural practices used for all soil-infecting diseases are essential. 



