200 ANNUAL KEPORTS OF DEPARTMENT OF AGRICULTURE. 



coiniHon Avhoat-scsib organism (i'/bherclla saub'mctu. It was ropcat- 

 (mIIv found producing spores in great abundanco on old coi-nslalks in 

 wheat Holds where corn had been the preceding ci'op. It occurs also 

 on other crop refuse, such as grain and grass stubble. Investigations 

 indicate that infected seed is the source of infection for the seedling 

 blight referred to above but is not an important souito for head 

 bli<dit. 



Infuence of soil temperature. — Soil temperature following seeding 

 time has an important influence on the development of seedling 

 blight of wheat wherever the organism is present. Less seedling 

 blight occurred when sowings were made in cool soil than when 

 they were made where the soil temperatures were comparatively high. 



Control mea.nires. — The control of blight, or scab, of wheat, as well 

 as that of other cereals, is not simple. In the case of wheat, the best 

 possible seed of the best adapted variojty should be obtained, thor- 

 oughly cleaned, and given tlie formaldehyde seed treatment. It 

 should then be sown when the soil is comparatively cool on land free 

 from old infected cornstalks. Crop refuse and grasses at the edges 

 of the field and in near-by waste places should be cleaned up. There 

 is some indication but no conclusive proof that some wdieat varieties 

 are less susceptible than others. 



TAKE-ALL DISEASE OF WHEAT. 



Occurrence and seventy of take-all. — This disease recurred to a 

 limited extent in both Illinois and Indiana in 1920. In the few cases 

 where the highly susceptible varieties of wheat were sown, the disease 

 was very severe, causing a reduction in yield of about 75 per cent. 

 Fortunately^ but very little seed of these varieties of wheat was sown 

 in the infested sections. 



Resistant and susceptible laheat varieties. — An extensive series of 

 wheat varieties was grown to determine their comparative suscepti- 

 bility. The so-called Salzer's Prizetaker and the Red Cross varieties 

 showed a very high degree of susceptibility: Illini Chief was moder- 

 ately affected, wdiile no other varieties showed more than 2 per cent of 

 infection and several were entireh'^ free from the disease. Among 

 the standard varieties which are either highly resistant or immune 

 are Turkey. Red May, and Red Wave. The use of the best adapted 

 of these varieties in the infested areas is the most practicable means 

 of controlling the disease. The regulations being enforced in the 

 infested areas do not permit the sowing of th" susceptible varieties 

 named. 



FLAX DISEASES. 



TWO TYl'KS i)V CANKKR ON I-LAX. 



Investigations in cooperation with the North Dakota. Agricultural 

 Ex])eriment Station have shown that there are two distinct types 

 of the so-called flax canker, one of a nonparasitic nature and the 

 other caused by a parasitic fungus. The nonparasitic type usually 

 is most conspicuous in flax-growling sections of North Dakota and 

 Montana. It manifests itself by enlargement of a portion of the 

 base of the stem and a weakening of the stem just below this enlarge- 

 ment, so that the attacked plants usually break over and become 



