195 



8 counties and including 303.5 acres, an average of 5.36 per cent of the 

 plants were affected with rot. 



Control of these diseases lies in the selection of disease-resistant 

 varieties and the use of disease-free seed, the balancing of nutritive ele- 

 ments in the soil, and the use, in some cases, of seed treatments. 



Corn Smut 



Caused by Ustilago zcac (Beck.) Ung. 



This is the most conspicuous of the corn diseases. All aerial parts 

 of the corn plant are subject to its attack. In its final stage it results 

 in the production of large malformations filled with smutty black powder 

 each grain of which is a spore capable of reproducing the disease. 



The annual crop reductions from this disease during a 5-year period 

 varied, according to the estimates shown in Table 27, from 1.5 per cent 

 to 3.5 per cent. While the mere statement of so small a percentage each 

 year is not impressive, the equivalent reduction in bushels, from seven 

 to twelve million, is startling. 



The first record of corn smut in Illinois is found in a collection by 

 A. B. Seymour at Camp Point, Adams county, in 1879. The disease 

 was collected again in 1881 in McHenry, Piatt, McLean, and Cham- 

 paign counties by Seymour. Subsequent collections show the presence 

 of smut in Champaign county in 1890, 1891, 1893, 1895, 1896, and 1897. 



These early records are sufficient to show that corn smut had at' 

 tained a rather wide distribution in the state a quarter of a century ago. 



The present known occurrence of this disease in Illinois is shown on 

 Map 18. It is apparent that it is prevalent in all parts of the state. 

 However, as the map indicates, it is most abundant and most prevalent 

 in a region running east and west through central Illinois. This region 

 is the "corn belt" of the state, and it is here that corn smut is of great- 

 est importance. In 1922 it was found in 55 of the 102 counties of the 

 state. During tfiat season it appears to have been especially prevalent in 

 the southern lip of the state and throughout the northwest. 



iMcld observations in 1923 in 26 fields (GIS acres) scattered through 

 17 representative counties indicated an average of 7.35 per cent of smut- 

 led plants. Probably this is not indicative of the seriousness of infec- 

 tion throughout the state, since in making the notes from which the 

 figures are drawn, corn in all .stages of development was seen. 



There is lilllc evidence of resistance among the corn varieties seen. 

 Under favoring conditions, however. Democrat corn always appears 

 more severely smutted than other kinds. 



Very little can be done in the control of corn smut. The fungus 

 ajjpcars able to live through the winter in manure and in corn refuse, 

 so that there is an abundance of infectious material ready to attack the 

 new crop. Wider sjjacing of plants for more thorough ventilation, later 



