194 



smut, rust, and a long list of others generally grouped under the inclusive 

 list "root-, stalk-, and ear-rots." Among this group are diseases result- 

 ing from a number of parasitic and semi-parasitic fungi, and at least two 

 kinds of bacteria. Recognition of these diseases is, even to experts, often 

 a difficult matter. 



The losses from corn diseases in Illinois are almost beyond estima- 

 tion, affecting, as they do, not only the ultimate yield from the stand, but 

 the development of the stand itself. Crop reductions from all reported 

 diseases during the years 1917-1923 inclusive, have been estimated, as 

 indicated in Table 25, to have varied from 2 per cent in 191T to 20.5 per 

 cent in 1923. The cash value of these reductions would vary between 

 seven and fifty-six million dollars. 



Root-, Stalk-, and Ear-Rots 



Included in this category are a number of diseases the nature of 

 which is not entirely understood. Among the fungi responsible are 

 Gibbcrclla satibinctii (Mont.) Sacc, Fusarinm inoiiilifoniic Shel., and 

 Diplodia ceae (Schw.) Lev. Despite the little knowledge of these dis- 

 eases now at hand, they are among the most important affecting corn, 

 and well deserve the amount of attention they are now receiving at the 

 hands of investigators. 



Estimates of crop reductions from these diseases have been made for 

 1918-1923 inclusive, and are brought together in Table 26. These esti- 

 mates range from 3 per cent in 1918 to 15 per cent in 1923, or from 

 10,870,000 to 59,525,000 bushels and the valuations for the G-year period 

 ranged from $7,385,000 to $38,691,000. Large as these estimates may 

 seem they are probably far below the actual loss. 



Root- and stalk-rots of corn are chiefly caused by the fungi Fiisariitm 

 monUiformc, Diplodia zcac, and Gibbcrclla sanbiiictii. The degree of in- 

 jury done by these organisms is dependent upon the relative susceptibility 

 of the corn plant in the various stages of its development and the effects 

 of the attack appear as rotted roots, barren stalks, or poorly tilled ears. 



Ear-rots are due to the same fungi as the root-rots, but the impor- 

 tance of the fungi is in the following order : Diplodia, Gibbcrclla. and 

 Pusariiiin. 



The dry car-rot caused by Dipolodia ccac is the source of consider- 

 able damage each year. In 1911 Burrill recorded the |irescnce of this 

 rot in 14 counties scattered throughout central Illinois. lie estimated the 

 damage to be from 1 per cent to 5 per cent, and noted that there wa^• very 

 little of this disease in the extreme northern and .southern sections of the 

 state. In 1912 he recorded it as having been more prevalent than in 1911. 



The distribution of these various rot-diseases of com in Illinois is 

 probably wide-spread. So far as known to us, it is shown on Map 17. 

 Tlie 1923 observations, while not capable of a statistical summary., show 

 the severitv of these diseases to be very great. In 15 fields examined in 



