Pests and Diseases 201 



Duggar l describes it as follows : " It begins to mani- 

 fest itself as a rule in August by blackening and drying 

 of the younger heart leaves, and later older leaves also 

 succumb, so that before the period of harvesting all the 

 leaves may be dead and merely the beet stub remain. 

 In cases where the beets are grown for seed, the fungus 

 may also be found upon the seed stalks and cases. It is 

 thought that this is one means by which the fungus may 

 pass over from one year to the next. From affected leaves, 

 particularly along the course of the fibrovascular bundles, 

 the browning and general discoloration of the tissues extend 

 into the tissues of the root, and there rot sets in. If the 

 disease begins early in the season great injury may be done. 



"Spraying experiments have not yet given complete 

 satisfaction. Care should be taken to destroy such re- 

 mains of the previous crop as is practical, and the treat- 

 ment of seed with Bordeaux mixture is desirable where 

 disease abounds." 



One company has adopted the practice of treating the 

 seed where more than 25 per cent shows infection. The 

 entire question of treating seed for this disease is at pres- 

 ent somewhat unsettled. 



Scab (Oospora scabies Thaxt.). 



In some sections sugar-beets are affected by a scab 

 similar in appearance to that on the potato and caused by 

 the same organism. It usually covers the beet more com- 

 pletely than it does the potato. The disease begins as 

 small irregularities on the surface of the beet in which a 

 corky, or spongy, appearance is seen. These small patches 



i Duggar, B. M., "Fungous Diseases of Plants." (1909), p. 3. 



