187 



practically coextensive with wheat-growing. When heads begin to ma- 

 ture, a pink moldy growth may be seen at the base of infected spikelets. 

 These spikelets turn yellow or brown, ripening prematurely, and the grain 

 which they bear is shriveled and often fungus-covered. 



The first record of the occurrence of scab in Illinois is its presence 

 near Kappa, Woodford county, in 189(3. The next definite record is by 

 H. W. Anderson, who reported it in 1918 as "unusually severe," causing 

 5 per cent loss near Decatur and some damage in Rock Island, Winne- 

 bago, and Lake counties. As indicated on Map 8, it is known to occur at 

 the present time in 45 counties, most of which lie in central and southern 

 Illinois. Their general distribution suggests, however, that this disease 

 occurs over the entire state. 



The importance of scab as a wheat disease in Illinois during the 

 years 1911-1923 inclusive is indicated by the estimated losses shown in 

 Table IT, which range from 1 per cent or 616,000 bushels in 1918 to 18 

 per cent or 15,156,000 bushels in 1919. 



During 1922 this disease was not found in great abundance in the 

 fields of the state, but in 1933 it appeared to be more prevalent. An ex- 

 amination of 2050 acres of wheat distributed among 24 counties in 1923 

 revealed a scab infection involving 3.26 per cent of the heads, on each of 

 which 51.14 per cent of the spikelets were diseased, which indicates a 

 loss of 1.66 per cent of the crop in the fields examined. This, however, 

 includes all the observations made during the season, and it is probable 

 that the early reports are not as typical as the more severe infections found 

 later in the season. 



A considerable difference in the amount of scab infection was ob- 

 servable on difi^erent varieties of wheat. Eight varieties on which special 

 observations were made showed an average infection of 2.3 per cent, as 

 indicated in Table 18, with individual varieties varying in amotmt of in- 

 fection from 0.248 per cent to 6.43 per cent. The average percentage 

 of infection on five varieties was less, and on three varities more, than 

 the average for all as shown in Table 19. The amount of dejjarture from 

 the average varied from 2.05 per cent less in the case of New Columbia 

 to 4.13 per cent more in the case of Turkey Red. Varieties indicated in 

 Table 19 as having infections less than the average should be useful in 

 regions where scab is serious. 



The fungus causing scab on wheat also causes a serious corn dis- 

 ease, and it has been demonstrated that the disease lives in the soil on corn 

 debris. For the prevention of serious losses from scab it is important 

 to select varieties of wheat showing a degree of resistance to the disease, 

 to employ a rotation scheme calling for the separation of wheat and corn 

 on the same land by at least one year's planting of a non-susceptibic crop, 

 and to use particular care in field culture, seeing that corn stalks arc either 

 removed or completely plowed under. 



