170 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



the Indiana Agricultural Experiment Station. Special studies to 

 discover biologic forni of leaf rusts have so far given negative re- 

 sults. Considerable progi-ess has been made in determining the hosts 

 and host relationships of the several leaf rusts, and niany data have 

 been obtained on factors influencing the development of epidemics. 

 Investigations have shown that the leaf rusts of wheat and rye can 

 overwinter in the urediniospore stage, even in the severe northern 

 winters. 



One of the most important discoveries in the history of rust inves- 

 tigations in this country has been made in cooperation with the 

 Agricultural Experiment Station of Kansas. The three Kansas 

 wheat selections of the Crimean group Kanred (P-T*26), P-1066, 

 and P-1068 which previousl}^ were known to be resistant to the 

 most seriously destructive biologic form of black rust, here proved to 

 be highly resistant also to leaf rust. 



FUSARIUM ROTS OF CORN AND THE SCAB OF WHEAT AND OTHER CEREALS. 



Investigations show that the Fusarium rots of corn Yiyc through the 

 winter both in the soil and in and on the seed. They attack the corn 

 crop at several different stages and in several different ways, as fol- 

 lows: (1) By preventing germination in laboratory and field; (2) 

 by causing a weak germination in the germinator and in the field; 

 (3) by blighting and destro3'ing the seedlings; (4) by dw^arfing the 

 seedlings so much that they develop only barren stalks or stalks 

 with small and sometimes almost w^orthless ears; and (5) by rotting 

 the root systems, or the stalks and ear shanks, resulting in stalks 

 easily blown over by Avind, in broken stalks, broken ear shanks, and 

 the rotting of the ears themselves in varying degTee. Some of the 

 diseased plants ripen prematurely. Because of this early ripening, 

 the ears from such plants frequently are selected for seed. Diseased 

 stalks may bear undiseased ears, but usually plants grown from such 

 ears are highly susceptible to attacks from the Fusarium rot fungi in 

 the soil or elsewhere. The diseased ears can be largely excluded from 

 seed corn by carefully selecting well-matured ears on healthy j)l^nts 

 in the field and by special study of such seed on the germinator. Pre- 

 liminary experiments show that by rejecting diseased ears the yields 

 of corn may be materially increased, possibly as much as 10 or 15 

 or even 20 per cent in portions of the corn belt. 



'Six species or fungi making the problem complex. Investiga- 

 tions to date indicate that there are at least six species and varieties 

 of fungi which cause rots of corn, and one of these also causes scab, 

 or blight, of wiieat and other cereals. There are tw^o important 

 sources of infection for both corn and Avhoat infected seed and old 

 infected cornstalks; there may be still other sources of infection of 

 wheat not yet determined. 



TAKE-ALL AND FLAG SMUT OF WHEAT. 



In April, 1919, the attention of tlie Bureau of Plant Industry was 

 called to a serious outbreak of disease in the wheat fields of Madi- 

 son County, 111. Prompt investigation discovered a disease very 

 similar to take-all, a very destructive disease of wheat in Australia 

 and other parts of the Orient, as well as in some countries of Europe. 



